Human p32: A Coactivator for Epstein–Barr Virus Nuclear Antigen-1-Mediated Transcriptional Activation and Possible Role in Viral Latent Cycle DNA Replication

Abstract

The Epstein-Barr virus (EBV) nuclear antigen-1 (EBNA-1) is required for the maintenance of the viral chromosome in latently infected, proliferating cells and plays a role in latent cycle DNA replication. EBNA-1 also functions as a positive and negative regulator of EBV gene expression. We have investigated the interaction of EBNA-1 with p32, a host mitochondrial protein that associates with EBNA-1 in EBV-positive Burkitt's lymphoma cells. Using a chromatin immunoprecipitation assay, we found that a fraction of p32 localizes to the viral latent cycle origin of DNA replication oriP in vivo. p32 binds EBNA-1 independently of other proteins or DNA. EBNA-1 variants lacking one of two p32 binding elements did not interact stably with p32 in cultured cells and were defective for both transcriptional activation of a reporter gene linked to oriP FR and replication and/or maintenance of a plasmid bearing oriP. These results support a role for p32 in transcriptional activation by EBNA-1 and suggest that p32 plays a role in EBV latent cycle DNA replication.

p32 (gC1qBP) Is a General Protein Kinase C (PKC)-binding Protein

“…In addition, a salient finding obtained here is that p32 is transiently translocated to the cell nucleus in response to TPA treatment, co-localizing there with PKC, and detected as a nucleoplasmic speckled pattern, typical of nucleoplasmic small nuclear ribonucleoprotein particles. This location is therefore consistent with the functional proposed roles for p32 in transcriptional regulation of viral gene expression (24) and as a regulatory factor of RNA splicing by inhibiting ASF/SF2 RNA binding and phosphorylation (23). There has been some controversy regarding the subcellular localization of p32.…”

“…Originally, p32 was characterized as a component of the AS/SF2 splicing activity purified from HeLa cells (20). Subsequent studies have shown that the molecule interacts with several cellular and viral proteins that participate in mitochondrial function (21, 22), transcription, and splicing factor modulation (23,24). Since the original study, it has become apparent that p32 is an evolutionarily conserved eukaryotic protein.…”

Mitotic chromosome interactions of Epstein-Barr nuclear antigen 1 (EBNA1) and human EBNA1-binding protein 2 (EBP2)

“…However, the degree to which each is involved in chromosome interactions in the context of the native EBNA1 protein is unclear. The similarity of the sequences in these Gly-Arg regions to AT hook sequences has led to the hypothesis that these sequence might directly contact chromosomal DNA (Sears et al, 2004), although the same sequences are known to interact with at least a few different cellular proteins (Holowaty et al, 2003;Shire et al, 1999;Snudden et al, 1994;Van Scoy et al, 2000;Wang et al, 1997).…”

The Ustilago maydis a2 Mating-Type Locus Genes lga2 and rga2 Compromise Pathogenicity in the Absence of the Mitochondrial p32 Family Protein Mrb1

“…The founding member of this protein family is the human p32 protein, which was originally identified in association with the SR family splicing factor ASF/SF2 (Krainer et al, 1991). p32 family proteins are implicated in diverse regulatory processes, including transcriptional activation by cooperating with viral transcription factors, pre-mRNA splicing, and mitochondrial RNA editing (Krainer et al, 1991;Yu et al, 1995;Petersen-Mahrt et al, 1999;Van den Brulle et al, 1999;Van Scoy et al, 2000;Hayman et al, 2001 and references therein). Because the function of p32 family proteins has not yet been addressed in a pathogenic fungus, we became interested in analyzing a possible regulatory function of Mrb1 connected to pathogenicity.…”