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1,2
* Cell Metabolism and Pharmacokinetics Laboratory, Regina Elena Cancer Institute, 00158 Rome, Italy;
Department of Experimental Medicine, University of L’Aquila, 67100 L’Aquila, Italy; and
Istituto di Tecnologie Biomediche, CNR, 00137 Rome, Italy
1Correspondence: Cell Metabolism and Pharmacokinetics Laboratory, Regina Elena Cancer Institute, Via Delle Messi d’oro 156, 00158 Rome, Italy. E-mail: fanciulli{at}crs.ifo.it; Istituto di Tecnologie Biomediche, CNR, Viale Marx 43, 00137 Rome, Italy. E-mail: passananti{at}itbm.rm.cnr.it
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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-factor 70 and SV40 large T antigen. In addition, we report that
Che-1 interacts with the retinoblastoma susceptibility gene (Rb) by two
distinct domains. Functionally, we demonstrate that Che-1 represses the
growth suppression function of Rb, counteracting the inhibitory action
of Rb on the trans-activation function of E2F1. These
results identify a novel protein that binds Rb and the core of pol II,
and suggest that Che-1 may be part of transcription regulatory
complex.—Fanciulli, M., Bruno, T, Di Padova, M., De Angelis, R.,
Iezzi, S., Iacobini, C, Floridi, A., Passananti, C. Identification of a
novel partner of RNA polymerase II subunit 11, Che-1, which interacts
with and affects the growth suppression function of Rb.
Key Words: RNA polymerase II • hRPB11 • Che-1 • Retinoblastoma susceptibility gene
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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. Despite
the fundamental role of pol II in initiation, elongation, and
termination of mRNA transcription, little is known about the specific
functions of its individual subunits, associations between subunits, or
possible contacts between subunits and RNA polymerase holoenzyme
components or transcription factors. Some evidence suggests that pol II
in yeast may influence gene expression by altering its subunit
composition in response to nutrient or thermal stress
(2
3
4)
. The issue of subunit variation of mammalian pol
II, however, has not been yet investigated. We have previously cloned
the pol II subunit hRPB11 and have shown the involvement of this
protein in dox-mediated cellular toxicity and cellular differentiation
(5
6
7)
. hRPB11 contains two amino acid sequences (
motif) with limited homology to the subunit of Escherichia
coli RNA polymerase, and we have shown that it interacts with
hRPB3, another human RNA pol II -like subunit (6)
. The
hRPB11 amino-terminal motif is necessary for this interaction and
it appears to be the unique contact site of hRPB11 with pol II. The
heterodimer hRPB11/3 is considered the functional counterpart of the
bacterial subunit homodimer (8
, 9)
. The eubacterial
subunit performs at least three critical functions: it serves as
the initiator for RNA pol assembly, it participates in promoter
recognition by sequence-specific protein–DNA interaction, and it is
the target for transcriptional regulation by binding to a specific set
of transcriptional activator proteins (10
11
12)
. To better
understand hRPB11 function, the yeast two-hybrid protein interaction
system was used to search for proteins that associate with hRPB11. The
screen resulted in the identification of a novel human protein, Che-1
(the sequence of the rat homologue of Che-1, named AATF, was recently
deposited in GenBank; accession number: AJ238717). This protein
shares homology with SV40 large T antigen and with E. coli
-factor 70. We provide evidence that Che-1 binds Rb in
vitro and in vivo. Moreover, we clearly demonstrate
that Che-1 affects the growth suppression function of Rb by relieving
its inhibitory effect on E2F1 trans-activating function and
implicating Che-1 in the regulation of the cell cycle. |
MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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. Three constructs carrying different hRPB11
amino-terminal deletions used in two-hybrid assay have also been
described (6)
. The construct 11Que, carrying a deletion of
the last 30 amino acid of hRPB11, was generated by polymerase chain
reaction (PCR) and cloned in frame in the pGBT9 vector. For two-hybrid
analysis of the Che-1/Rb interaction, Che-1 portion from aa 248 to aa
476 and the complete ORF of Rb were cloned into pGBT9 and pGAD424
(Clontech), respectively.
Che-1 cloning and expression constructs
The partial cDNA sequence encoded by the clone isolated from the
two-hybrid screen was extended using 5' Marathon RACE reaction
(Clontech) on human skeletal muscle mRNA, following the conditions
detailed by the manufacturer. The complete ORF was amplified by PCR and
cloned into a pCS-MT myc-tagged mammalian expression vector and into
pGEX4T3 (Bio-Rad, Hercules, Calif.) to generate a
glutathione-S-transferase (GST) -Che-1 fusion protein. The complete ORF
of Rb was generated by PCR and cloned into pcDNA3 (Invitrogen, San
Diego, Calif.) mammalian expression and pGEX4T1 (Bio-Rad) vectors.
hRPB11 and its deletions were fused to GST cloning in pGEX4T1 vector
the same inserts contained in pGBT9 constructs. The construct carrying
hRPB11 fused to 6xHis tag has been already described (5)
.
E2F1 mammalian expression vector and DHFR-luciferase vector were a kind
gift from Prof. Levrero (University of Rome, ‘La Sapienza’). Che-1
fragments and deletions mutants were produced by PCR and cloned into
the pCS-MT vector, which contains the Sp6 binding site. All constructs
produced were sequenced by Sequenase reaction (Amersham, Arlington
Heights, Ill.) according to the manufacturer’s instructions.
Northern blot analysis
Filters containing poly(A)+ RNA from 16
normal human tissues (Clontech) were hybridized with
32P-labeled Che-1 cDNA using Quikhyb (Stratagene,
San Diego, Calif.) according to manufacturer’s instructions.
Purification of GST fusion proteins and in vitro
protein interaction
BL21 bacteria strain was transformed with GST fusion protein
constructs and the proteins were purified on glutathione-Sepharose
resin (Pharmacia, Piscataway, N.J.). For protein–protein interaction
assays, comparable amounts of resin-bound GST fusion proteins were
incubated with in vitro-translated proteins in NETN buffer
(20 mM Tris-HCl, pH 8.0, 100 mM NaCl, 1 mM EDTA, and 0.5% Nonidet
P-40) for 1 h at 4°C. The resins were then pelleted and
extensively washed in the same buffer. The bound proteins were
separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis
(SDS-PAGE); the gel was then fixed, incubated in Enlighting solution
(Du Pont, Wilmington, De.), dried, and exposed for fluorography.
In vitro transcription and translation
In vitro transcription and translation were carried
out with TNT-coupled reticulocyte lysate systems (Promega, Madison,
Wis.) and L-[35S]methionine (>1000 Ci/mmol;
Amersham) according to the manufacturer.
Cells and transfections
Saos-2 and Cos7 cell lines were grown in Dulbecco’s modified
Eagle’s medium (DMEM), supplemented with 10% fetal calf serum, and
transfections were carried out by N,
N-bis-(2-hydroxiethil)-2-aminoethanesulfonic acid (BES) -calcium
phosphate precipitation as described (6)
. U2OS cells were
grown in RPMI 1640 medium supplemented with 10% fetal calf serum.
Immunoprecipitations and Western blot analysis
Cos7 transfected cells were rinsed three times with ice-cold
phosphate-buffered saline, harvested, centrifuged at 4°C, and cell
pellets were lysed by incubation at 4°C for 1 h in 500 µl
lysis buffer (50 mM Tris, pH 8.0, 250 mM NaCl, 10 mM
MgCl2, 1 mM PMSF, 10 mg/ml leupeptin)
supplemented with 0.2% Nonidet P-40. Supernatants were cleared by
centrifugation, precleared using 20 µl protein A/protein G beads
(Santa Cruz, Santa Cruz, Calif.), and immunoprecipitated by standard
procedures using mouse anti-myc monoclonal antibody clone 9e10
(Invitrogen). Western blots were prepared by standard procedures and a
mouse monoclonal antibody direct against Rb (PharMingen; San Diego,
Calif., cat. 14001) was used to detect Rb by chemiluminescence reaction
(Amersham). For Che-1 antiserum production, New Zealand rabbits were
immunized four times with 250 mg of the purified peptide
LVGLQUEELLFQYPDT (aa 287–301) every 2 wk using Freund’s adijuvants
(Difco, Detroit, Mich.); antiserum was collected 3 days after the last
injection. The specific polyclonal antiserum was purified by column
chromatography using the Che-1 peptide coupled to activated EAH
Sepharose. U2OS cells were lysed as described above. Supernatants
recovered and precleared were immunoprecipitated by anti-Rb monoclonal
antibody or anti-myc monoclonal antibody as a negative control. The
bound proteins were separated by SDS-PAGE, transferred to PVDF
membranes (Millipore), and probed with anti-Che-1 antibody.
Immunoreactivity was detected by chemiluminescence reaction. For Che-1
expression analysis, an equal amount (30 µg) of total proteins was
electrophoresed on 10% polyacrylamide gel, transferred to PVDF
membrane, and probed with anti-Che-1 antibody. Che-1 expression levels
were detected by chemiluminescent visualization. The relative intensity
of the bands was quantified by densitometric analysis and normalized to
the relative HSP70 protein levels detected using a specific monoclonal
antibody (Santa Cruz, cat. W27).
Luciferase activity assay
BES-calcium phosphate precipitation was used to transiently
transfect Saos-2 cells with DHFR luciferase reporter, the indicated
expression vectors, and with pCMVß-gal expression plasmid as an
internal standard. The transfection medium was replaced by DMEM
supplemented with 10% fetal calf serum 18 h after transfection.
After incubation for 48 h, luciferase was assayed using reagents
from Promega according to the manufacturer’s instructions.
ß-Galactosidase was assayed using a ß-galactosidase assay kit
(Tropix, Bedford, Mass.).
Colony-forming efficiency assay
Colony-forming efficiency assays were performed after
transfection of Saos-2 cells with the indicated expression vectors. All
the transfections were performed using the same amount of plasmids
carrying G-418 resistance. G-418 selection was initiated 2 days after
transfection; dishes were stained with methylene blue 14 days later.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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. A cDNA
fragment encoding the 117 amino acid residues of full-length hRPB11 was
fused in-frame with the yeast Gal4 DNA binding domain of the vector
pGBT9 (Clontech). Due to the high level of hRPB11 transcription in
human skeletal muscle, a two-hybrid cDNA library from this tissue was
screened. Thirteen positive cDNAs with different degree of interaction
with hRPB11 were isolated, and one clone of 1167 bp encoding a novel
protein, Che-1, was further characterized. To define whether the domain
of hRPB11 required for interaction with Che-1 was the same as that
involved in the binding to hRPB3, three progressive amino-terminal
truncated hRPB11 derivatives—11QUI, 11QUO, and 11QUA (Fig. 1A
)—were used in the yeast two-hybrid assay. All three
constructs retained Che-1 binding capacity (Fig. 1B
). In
contrast, 11QUE, a construct missing the hRPB11 leucine-rich
carboxyl-terminal motif (Fig. 1A
), was unable to
interact with Che-1 (Fig. 1B
). A two-hybrid screening,
performed using Che-1 as bait, isolated seven clones encoding hRPB11
(data not shown), thus confirming the interaction between these two
proteins. To confirm hRPB11-Che-1 binding in a cell-free system, we
prepared the complete hRPB11 coding sequence and its deletions in
E. coli as GST fusion proteins. These fusion proteins were
then tested for their ability to bind 35S-labeled
Che-1. Consistent with the two-hybrid assay, only the fusion proteins
containing the carboxyl-terminal motif of hRPB11 specifically bound
Che-1 (Fig. 1C
). We conclude, therefore, that hRPB11 binds
Che-1 both in vivo and in vitro through its
leucine-rich carboxyl-terminal motif.
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Characterization of Che-1
To assess the expression pattern of the Che-1 transcript,
32P-labeled Che-1 cDNA was used to probe multiple
tissue Northern blots. A single hybridizing signal of ~2.1 kb was
observed (Fig. 2A
), which was most abundant in heart, skeletal muscle, and
testis, thus resembling the pattern of hRPB11 expression
(5)
. The Che-1 cDNA isolated lacked an initiating
methionine codon and was therefore assumed to be partial. 5'-RACE, used
with human skeletal muscle cDNA to extend the Che-1 clone, resulted in
the addition of another 915 bp of novel sequence that, when finally
assembled, produced a Che-1 cDNA of 2082 bp consistent with the band
detected by Northern blot. An initiating methionine codon was located
174 bp from the 5'end producing a 558 amino acid open reading frame
(Fig. 2B
). Inspection of the predicted protein sequence
suggested a molecular mass of ~62.3 kDa. Che-1 is not homologous to
any previously described protein. Che-1 amino acid sequence analysis
revealed the presence of a canonical leucine zipper motif and three
nuclear receptor binding LXXLL consensus sequences (15
, 16)
distributed throughout the protein (Fig. 2B
).
Comparison by Genbank BLAST (14)
of the Che-1 protein
revealed a 32 amino acid fragment of relevant homology between Che-1
and E. coli -factor 70 (Fig. 2C
). Moreover,
two short domains of homology to SV40 early gene large T were also
observed (Fig. 2C
). The production of an affinity-purified
polyclonal antibody anti-Che-1 allowed a Western blot analysis of this
protein, confirming its molecular weight (Fig. 2D
). Che-1
resulted expressed in all human cell lines examined except Saos-2
cells.
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Che-1 interacts with Rb
It has previously been demonstrated that simian virus 40 large T
antigen can form complexes with the Rb gene product by a consensus Rb
binding sequence L-X-C-X-E (17
18
19)
. Since Che-1 shares a
region of strong homology with large T of SV40, partially overlapping
Rb binding region, we tested whether Che-1 protein has the capacity for
direct and specific interaction with Rb.
35S-labeled Rb protein was incubated with
bacterial recombinant GST and GST-Che-1 fusion proteins. Figure 3A
shows that although GST control protein did not bind Rb,
GST-Che-1 was able to bind Rb. Consistent with these results, GST-Rb
was also able to interact specifically with
35S-labeled Che-1 (Fig. 3B
). To
provide evidence that Che-1 also associates with Rb protein in
vivo, expression vectors for Rb and myc-tagged Che-1 were
cotransfected into COS7 cells. Immunoprecipitation of tagged Che-1,
followed by Western blot analysis of the precipitants for the presence
of Rb, was indicative of an interaction with both iper-phosphorylated
and ipo-phosphorylated forms of Rb, although this last form was clearly
present in a larger amount. Myc-tag alone showed no binding to Rb (Fig. 3C
). Next we asked whether Che-1 and Rb could
coimmunoprecipitate without overexpression of the proteins. Extracts
from U2OS human cells were immunoprecipitated with anti-Rb antibody and
the precipitated proteins were assayed by Western blot for the presence
of Che-1. The results demonstrate that a relevant amount of cellular
Che-1 is indeed complexed with Rb protein (Fig. 3D
),
indicating a physiological interaction between Che-1 and the tumor
suppressor Rb. This specific interaction was further confirmed in a
two-hybrid assay performed by cotransforming Rb fused to the activation
domain of Gal4 with pGBT9/Che-1 or with pGBT9/lamin and pGBT9 empty
vector as negative controls. Figure 3E
shows that whereas
pGBT9/Che-1 was able to bind Rb, pGBT9/lamin and pGBT9 empty vector did
not show any significant interaction.
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Che-1 contacts hRPB11 and Rb with different protein regions
To test the possibility that Che-1 may mediate complex formation
between hRPB11 and Rb proteins via direct contact, we determined the
regions of Che-1 involved in these interactions. Using a series of six
polypeptides covering the whole Che-1 protein, we performed in
vitro transcription/translation and GST pull-down assays. Two
Che-1 sequential peptide fragments 271–370 and 371–470 were able to
bind GST-Rb fusion protein (Fig. 4A
), indicating the presence of two distinct domains involved
in the contact with Rb. Since peptide 271–370 could also bind
GST-hRPB11, to determine whether GST-hRPB11 and GST-Rb compete for the
same binding site within Che-1 fragment 271–370, we further divided
this region into two smaller polypeptides. As shown in Fig. 4B
, two distinct Che-1 domains are involved in the
interaction with hRPB11 and Rb, respectively. The fragment 271–313,
containing the putative leucine zipper region (Fig. 2B
), is
responsible for hRPB11 binding. This finding is consistent with the
presence of a leucine-rich motif within the carboxyl-terminal of
hRPB11 responsible for the binding to Che-1. It is noteworthy that the
Che-1 fragment 314–370, which also interacts with Rb, possesses the
extensive homology to the SV40 large T early gene (Fig. 2C
).
Since these interacting regions are adjacent, it is still possible that
the binding of Rb with Che-1 displaces it from hRPB11. To test this
hypothesis, we performed a pull-down experiment using 6xHis-hRPB11
bound to Ni-NTA agarose beads and
35S-labeled-Che-1, incubated with eluted GST-Rb
or GST, as control. Figure 4C
shows that the presence of Rb
did not decrease the ability of Che-1 to contact hRPB11. Therefore, we
conclude that Che-1 binds hRPB11 and Rb by different protein regions
(Fig. 4D
).
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Che-1 affects the inhibitory effect of Rb on E2F1
The binding of Che-1 to Rb may have important implications for the
functions of this protein. Rb interacts with E2F1, a transcription
factor critical for G1/S transition, and suppresses its
trans-activating function (20
, 21)
. This
results a strong correlation between Rb/E2F1 complex formation and Rb
blockade of the G1/S transition (22
23
24)
. To assess
whether binding of Che-1 to Rb perturbs the regulation of E2F1
activity, Che-1, E2F1 and Rb mammalian expression plasmids were
cotransfected with an E2F1 reporter vector (DHFR-luciferase)
(25)
into human Rb-negative Saos-2 cells. This experiment
resulted in significant reduction of the inhibitory effect of Rb on
E2F1 trans-activating function (Fig. 5A
). This inhibition of Rb repression by Che-1 was also
observed when a Gal4-E2F1 fusion and a Gal4-dependent reporter were
used (data not shown). These results are consistent with Che-1/Rb
complex formation relieving the suppression of E2F1
trans-activating function or stimulation of E2F1 activity by
a Rb-independent phenomenon. The latter hypothesis was abandoned when
we tested the ability of Che-1 to stimulate E2F1 reporter activity.
Figure 5B, C
shows that Che-1, when transfected alone or
cotransfected with E2F1, did not significantly increase either basal
transcription independent of E2F1/Rb activity or E2F1
trans-activating function in the absence of Rb. On the basis
of these results, it seems that the activation of E2F1 by Che-1 may
depend on the ability of Che-1 to form a complex with Rb. In this case,
then, one would expect Che-1 mutants lacking the Rb binding sites to be
defective in E2F1 activation. We therefore tested two Che-1 mutants
(Fig. 5D
) in an E2F1 repression assay. Figure 5C
shows that the mutant 
1 lacking the Che-1 region 371–558 did not
significantly inhibit Rb repression of E2F1 activity. Consistent with
this finding, the Che-1 mutant 2 lacking both Rb binding regions of
Che-1 did not counteract the activity of Rb on E2F1.
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Che-1 inhibits the growth suppression activity of Rb
To further analyze the effect of Che-1 on Rb activity, a
colony-forming efficiency assay was performed. Parallel plates
containing the same number of Saos-2 cells were transfected with Rb and
Che-1 expression plasmids, selected with neomicin, and the number of
colonies per plate was screened 14 days later. Figure 6
shows representative plates (Fig. 6A
) and colony counts
(Fig. 6B
) from these experiments. When transfected with Rb,
Saos-2 cells showed a ~60% reduction in colony-forming efficiency
compared to cells transfected with the empty vector. Cells
cotransfected with Rb and Che-1 showed only a 27% reduction, whereas
cells transfected with Che-1 alone did not exhibit further changes in
colony-forming efficiency. Consistent with the results on E2F1
activity, Che-1 mutants lacking the Rb binding sites did not show any
effect on growth suppression activity of Rb.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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. Besides the well-documented transcriptional
regulatory role of the carboxyl-terminal domain of the largest subunit
(26
, 27)
, other subunits of pol II have been shown to be
potential targets for transcriptional regulators (28
29
30
31
32)
.
We and others have recently demonstrated the interaction between hRPB11
and hRPB3 (6
, 33
34
35)
, indicating a fundamental structural
role for this heterodimer. On the other hand, the involvement of hRPB11
in dox-mediated cellular toxicity and cellular differentiation suggests
an additional regulative role for this subunit. Here we describe the
isolation and characterization of Che-1, a novel partner of hRPB11.
Che-1 interacts with the hRPB11 carboxyl-terminal motif, which is
distinct from the hRPB3 binding domain (6)
. Thus, it is
possible that hRPB11 can bind to hRPB3 and to Che-1 simultaneously,
acting as a bridge between Che-1 and pol II. Che-1 has a molecular mass
of ~62.3 kDa and is not homologous to any previously described
protein. Consistent with the interaction to hRPB11, Che-1 shares a
domain of striking homology with E. coli RNA polymerase
-factor 70, supporting the hypothesis that Che-1 could be a
component of the pol II holoenzyme. In addition, analysis of Che-1
amino acid sequence reveals the presence of several potential
protein–protein interaction domains, suggesting that Che-1 brings
different signaling molecules to the pol II.
Here we provide evidence that Che-1 interacts with Rb protein, and as such could represent the first described link between Rb and the core of pol II. Two distinct portions of Che-1 protein mediate interaction with Rb; significantly, one of them contains a relevant homology with SV40 large T. The binding of Che-1 to Rb affects the growth suppression function of Rb by in part relieving its inhibition of E2F1 transcriptional activity. In fact, Che-1 mutants lacking Rb binding domains did not affect the activity of Rb on E2F1. Thus, our data indicate that Che-1 binds Rb and perturbs its growth suppression function.
Rb represses transcription by masking the E2F1
trans-activation (36)
, probably tethering the
E2F1 protein to histone deacetylase HDAC1, forming a complex that
prevents expression from E2F-bound promoters (37
38
39)
. On
the basis of these observations, we could assume that Che-1 exerts its
function by recruiting pol II and displacing Rb from E2F1.
Alternatively, Che-1 could compete with HDAC1 for the Rb binding site,
thus removing HDAC1 from the complex Rb-E2F1. Additional experimental
data will provide new evidence to confirm or invalidate these
hypothesis and to better characterize the role of Che-1 on the
regulation of transcription.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Received for publication October 30, 1999. Revised for publication November 24, 1999.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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-like subunits of Arabidopsis thaliana RNA polymerase II. J. Biol. Chem. 271,5085-5094This article has been cited by other articles:
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  F. De Nicola, T. Bruno, S. Iezzi, M. Di Padova, A. Floridi, C. Passananti, G. Del Sal, and M. Fanciulli The Prolyl Isomerase Pin1 Affects Che-1 Stability in Response to Apoptotic DNA Damage J. Biol. Chem., July 6, 2007; 282(27): 19685 - 19691. [Abstract] [Full Text] [PDF]
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 M. G. Di Certo, N. Corbi, T. Bruno, S. Iezzi, F. De Nicola, A. Desantis, M. T. Ciotti, E. Mattei, A. Floridi, M. Fanciulli, et al. NRAGE associates with the anti-apoptotic factor Che-1 and regulates its degradation to induce cell death J. Cell Sci., June 1, 2007; 120(11): 1852 - 1858. [Abstract] [Full Text] [PDF]
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A. Robert, G. Margall-Ducos, J.-E. Guidotti, O. Bregerie, C. Celati, C. Brechot, and C. Desdouets The intraflagellar transport component IFT88/polaris is a centrosomal protein regulating G1-S transition in non-ciliated cells J. Cell Sci., February 15, 2007; 120(4): 628 - 637. [Abstract] [Full Text] [PDF]
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N. Corbi, T. Bruno, R. De Angelis, M. Di Padova, V. Libri, M. G. Di Certo, L. Spinardi, A. Floridi, M. Fanciulli, and C. Passananti RNA Polymerase II subunit 3 is retained in the cytoplasm by its interaction with HCR, the psoriasis vulgaris candidate gene product J. Cell Sci., September 15, 2005; 118(18): 4253 - 4260. [Abstract] [Full Text] [PDF]
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 W. J. Benga, S. Grandemange, G. V. Shpakovski, E. K. Shematorova, C. Kedinger, and M. Vigneron Distinct regions of RPB11 are required for heterodimerization with RPB3 in human and yeast RNA polymerase II Nucleic Acids Res., June 24, 2005; 33(11): 3582 - 3590. [Abstract] [Full Text] [PDF]
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S. Burgdorf, P. Leister, and K. H. Scheidtmann TSG101 Interacts with Apoptosis-antagonizing Transcription Factor and Enhances Androgen Receptor-mediated Transcription by Promoting Its Monoubiquitination J. Biol. Chem., April 23, 2004; 279(17): 17524 - 17534. [Abstract] [Full Text] [PDF]
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M. Di Padova, T. Bruno, F. De Nicola, S. Iezzi, C. D'Angelo, R. Gallo, D. Nicosia, N. Corbi, A. Biroccio, A. Floridi, et al. Che-1 Arrests Human Colon Carcinoma Cell Proliferation by Displacing HDAC1 from the p21WAF1/CIP1 Promoter J. Biol. Chem., September 19, 2003; 278(38): 36496 - 36504. [Abstract] [Full Text] [PDF]
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