Adenovirus DNA binding protein interacts with the SNF2-related CBP activator protein (SrCap) and inhibits SrCap-mediated transcription.
The SNF2-related CBP activator protein, SrCap (pronounced "sir cap"), shares homology with the SNF2/SWI2 protein family. SrCap was cloned through its ability to bind CBP. SrCap can function as a CBP coactivator and can activate transcription in a reporter assay when expressed as a Gal-SrCap fusion protein. A monoclonal antibody raised against the carboxyl terminus of SrCap coimmunoprecipitates CBP/p300, supporting the model that SrCap is a CBP binding protein and that these proteins can be found together in a cellular protein complex. In addition, several cellular proteins are coimmunoprecipitated by the SrCap-specific antibody. Since adenovirus E1A proteins interact with CBP/p300 proteins, we examined what proteins could be copurified in a SrCap-specific coimmunoprecipitation assay from lysates of adenovirus-infected cells. While E1A proteins were not detected in this complex, to our surprise, we observed the presence of an infected-cell-specific band of 72 kDa, which we suspected might be the adenovirus DNA binding protein, DBP. The adenovirus DBP is a multifunctional protein involved in several aspects of the adenovirus life cycle, including an ability to modulate transcription. The identity of DBP was confirmed by DBP-specific Western blot analysis and by reimmunoprecipitating DBP from denatured SrCap-specific protein complexes. Using in vitro-translated DBP and SrCap proteins, we demonstrated that these proteins interact. To determine whether this interaction could affect SrCap-mediated transcription, we tested whether increasing amounts of DBP could modulate the Gal-SrCap transcription activity. We observed that DBP inhibited Gal-SrCap transcription activity in a dose-dependent manner. These data suggest a novel mechanism of adenovirus host cell control by which DBP binds to and inactivates SrCap, a member of the SNF2 chromatin-remodeling protein family.
Xu
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Department of Molecular Microbiology and Immunology, St. Louis University Health Sciences Center, St. Louis, Missouri 63104, USA.
Chackalaparampil
I
I
Monroy
M A
MA
Cannella
M T
MT
Pesek
E
E
Chrivia
J
J
Yaciuk
P
P
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors*; D000818:Animals; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D050881:E1A-Associated p300 Protein; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D009687:Nuclear Proteins / Q000378:metabolism; D011233:Precipitin Tests; D015534:Trans-Activators / Q000378:metabolism; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000502:physiology*
C095599:DBP protein, Adenovirus; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D015534:Trans-Activators; D014764:Viral Proteins; D004247:DNA; D050881:E1A-Associated p300 Protein; C494361:Ep300 protein, mouse; D000251:Adenosine Triphosphatases; C119652:SRCAP protein, human