Protein kinase A associates with HA95 and affects transcriptional coactivation by Epstein-Barr virus nuclear proteins.
HA95, a nuclear protein homologous to AKAP95, has been identified in immune precipitates of the Epstein-Barr virus (EBV) coactivating nuclear protein EBNA-LP from EBV-transformed lymphoblastoid cells (LCLs). We now find that HA95 and EBNA-LP are highly associated in LCLs and in B-lymphoma cells where EBNA-LP is expressed by gene transfer. Binding was also evident in yeast two-hybrid assays. HA95 binds to the EBNA-LP repeat domain that is the principal coactivator of transcription. EBNA-LP localizes with HA95 and causes HA95 to partially relocalize with EBNA-LP in promyelocytic leukemia nuclear bodies. Protein kinase A catalytic subunit alpha (PKAcsalpha) is significantly associated with HA95 in the presence or absence of EBNA-LP. Although EBNA-LP is not a PKA substrate, HA95 or PKAcsalpha expression in B lymphoblasts specifically down-regulates the strong coactivating effects of EBNA-LP. The inhibitory effects of PKAcsalpha are reversed by coexpression of protein kinase inhibitor. PKAcsalpha also inhibits EBNA-LP coactivation with the EBNA-2 acidic domain fused to the Gal4 DNA binding domain. Furthermore, EBNA-LP- and EBNA-2-induced expression of the EBV oncogene, LMP1, is down-regulated by PKAcsalpha or HA95 expression in EBV-infected lymphoblasts. These experiments indicate that HA95 and EBNA-LP localize PKAcsalpha at nuclear sites where it can affect transcription from specific promoters. The role of HA95 as a scaffold for transcriptional regulation is discussed.
Han
Innoc
I
Ewha Institute of Neuroscience, Ewha University Medical School, Seoul 110-783, Korea.
Xue
Yong
Y
Harada
Shizuko
S
Orstavik
Sigurd
S
Skalhegg
Bjorn
B
Kieff
Elliott
E
D002352:Carrier Proteins / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019309:Epstein-Barr Virus Nuclear Antigens / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008957:Models, Genetic; D009687:Nuclear Proteins / Q000378:metabolism*; D016366:Open Reading Frames / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020449:Repetitive Sequences, Amino Acid; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D014763:Viral Matrix Proteins / Q000235:genetics; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
C490117:AKAP8L protein, human; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C402641:EBNA-2 protein, Human herpesvirus 4; C402640:EBNA-LP protein, Human herpesvirus 4; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D019309:Epstein-Barr Virus Nuclear Antigens; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D014763:Viral Matrix Proteins; D014764:Viral Proteins; C015482:protein kinase modulator; D017868:Cyclic AMP-Dependent Protein Kinases