Disease relevance of BMRF1

• LY294002 markedly down regulated expression of EBV lytic gene BRLF1 protein Rta, BMRF1 protein EA-D, but not BZLF1 protein ZEBRA [1].
• We found that low concentrations of epigenetic modifying agents, 5-aza-2'-deoxycytidine (5-aza-CdR) or trichostatin A (TSA), induced the expression of BMRF1, BZLF1, and BRLF1 genes, which are found in the lytic form of the virus, in an EBV-positive gastric cancer cell line [2].
• Unlike the herpes simplex virus UL42 homologue, BMRF1 was found to self-associate in solution [3].
• In this work, BMRF1 was purified directly from human cells infected with an adenovirus vector expressing the BMRF1 gene product [3].
• Purification and characterization of the DNA-binding activity of the Epstein-Barr virus DNA polymerase accessory protein BMRF1 gene products, as expressed in insect cells by using the baculovirus system [4].

High impact information on BMRF1

• Here we demonstrate that the retinoic acid receptor alpha (RAR alpha) and retinoid X receptor alpha (RXR alpha) inhibit the ability of the Z protein to transactivate the viral early promoter BMRF1, which directs transcription of EA-D [5].
• RXR alpha inhibits Z from binding to the AP-1 motif in the BMRF1 promoter and, reciprocally, Z inhibits RAR alpha from binding to its retinoic acid response element in the BRE promoter [5].
• Transactivation efficiency of the EBV BMRF1 promoter by Z is cell type dependent [6].
• In B cells, in which EBV typically exists in a latent form, Z activates the BMRF1 promoter inefficiently [6].
• Bromodeoxyuridine-labeled chromatin immunodepletion analyses confirmed that PCNA is loaded onto newly synthesized viral DNA as well as BALF2 and BMRF1 viral proteins during lytic replication [7].

Chemical compound and disease context of BMRF1

• Using the SNU-719 gastric cancer cell line, which is naturally infected with Epstein-Barr virus, we found that the chemotherapeutic agents, such as 5-fluorouracil, cis-platinum and taxol, induced the expressions of BMRF1, BZLF1 and BRLF1 proteins that are usually found in the lytic form of the virus [8].
• The Epstein-Barr virus (EBV) BMRF1 gene product is necessary for DNA polymerase catalytic subunit (BALF5) activity in 100 mM ammonium sulfate [9].
• Two specific FAS inhibitors, cerulenin and C75, prevent R activation of IE (Z) and early (BMRF1) lytic EBV proteins in Jijoye cells [10].
• The 1.34 kb BcII-BgIII-fragment of the BamHI-M region of Epstein-Barr virus genome, comprising the complete BMRF1 open reading frame, was cloned into the tryptophan regulated E. coli expression vector pATH1 [11].

Biological context of BMRF1

• Furthermore, the anti-PCNA, -MSH2, -MSH3, or -MSH6 antibodies could immunoprecipitate BMRF1 replication protein probably via the viral DNA genome [7].
• Despite the presence of an R binding site, the BMRF1 promoter is only moderately responsive to R alone in either HeLa or Jurkat cells [12].
• These observations strongly suggest that the presence of EBV DNA polymerase accessory protein, BMRF1 gene product, does influence the enzymatic properties of EBV DNA polymerase catalytic subunit [13].
• This same family of polypeptides was identified when the immunoblots were reacted with the R3 monoclonal antibody, and we concluded that this antibody also recognized the product of the BMRF1 open reading frame [14].
• In one orientation, termed BamHI-M rightward reading frame 1 (BMRF1), a set of phosphoproteins ranging in size from 47,000 to 54,000 daltons was synthesized [15].

Anatomical context of BMRF1

• We have previously demonstrated that these proteins cooperatively activate the EBV early promoter BMRF1 in lymphoid cells but not in epithelial cells [12].
• Efficient activation of the BMRF1 promoter by Z alone in HeLa cells requires two ZREs (located at -59 and -106), whereas two additional Z binding sites (located at -42 and -170) contribute very little to Z-induced activation [12].
• Here we demonstrate that BMRF1 activates transcription of the cellular gastrin gene in telomerase-immortalized keratinocytes [16].

Associations of BMRF1 with chemical compounds

• The addition of the BMRF1 polymerase accessory subunit to the reaction enhanced the double-strand exonucleolytic activity in the presence of high concentrations of ammonium sulfate (fourfold stimulation at 75 mM ammonium sulfate) [17].
• Glutathione S-transferase-Mta bound to BMRF1 and BMLF1 transcripts but not to a control cellular gene RNA [18].
• Inhibition of viral DNA replication with phosphonoacetic acid, a viral DNA Pol inhibitor, eliminated the DNA-bound form of the BMRF1 protein, although the protein was sufficiently expressed in the cells [19].
• In lymphoid cells, a Z mutant which has been altered at amino acid 200 (tyrosine to glutamic acid) transactivates both the early BMRF1 promoter and the immediate-early BZLF1 promoter (Zp) four- to fivefold better than wild-type Z [20].

Physical interactions of BMRF1

• These observations suggest that the BMRF1 polymerase accessory subunit forms a complex with the BALF5 polymerase catalytic subunit to stabilize the interaction of the holoenzyme complex with the 3'-OH end of the primer on the template DNA during exonucleolysis [17].

Regulatory relationships of BMRF1

• In contrast, BZLF1-induced activation of the BMRF1 promoter is inhibited in the presence of the BMRF1 gene product [21].
• The BMRF2 promoter may be regulated differentially from the BMRF1 promoter and more closely resembles that of BDLF3 [22].
• We demonstrate that a region of oriLyt (the "downstream component"), previously shown to be one of two domains absolutely essential for oriLyt replication, is required for BMRF1-induced activation of the BHLF1 promoter [23].

Other interactions of BMRF1

• Sequence analysis revealed that this clone contains about 75% of the BMRF1 and the complete BMRF2 open reading frames [24].
• Additionally, it was demonstrated that BGLF4 co-localizes with viral DNA polymerase processivity factor, EA-D (BMRF1), in the virus replication compartment and that it is a virion component [25].
• Optimal stimulation was obtained when the molar ratio of BMRF1 protein to BALF5 protein was 2 and higher, identical to the values required for reconstituting the optimum DNA polymerizing activity (T. Tsurumi, T. Daikoku, R. Kurachi, and Y. Nishiyama, J. Virol. 67:7648-7653, 1993) [17].
• Each of the replication-negative Zta variants was capable of transactivating expression from both BHLF1 promoter-chloramphenicol acetyltransferase constructions and the BMRF1 promoter on endogenous EBV genomes in Raji cells with efficiency comparable to that of the wild-type polypeptide [26].
• The use of the Z(S186A) mutant form of ZEBRA, whose transactivation function is manifest only by coexpression of Rta, allows identification of a second class of lytic cycle genes, such as BMRF1 and BHRF1, that are activated in synergy by Rta and ZEBRA [27].

Analytical, diagnostic and therapeutic context of BMRF1

• The Epstein-Barr virus polymerase accessory factor BMRF1 adopts a ring-shaped structure as visualized by electron microscopy [3].
• Lytic Zta and BMRF1 protein expression was detected by immunohistochemistry, and DNA PCR analyses estimated an EBV copy number of 300 to 600 genomes per infected cell [28].
• Site-directed mutagenesis of this region allowed us to separate the transactivator and nuclear localization motifs of BMRF1 [29].
• An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of IgA antibody to the BMRF1 protein of EBV in saliva and serum samples [30].
• Immunohistochemisty for viral BMRF1 and BZLF1 and in situ hybridization for lytic gene transcripts showed no evidence of replicative EBV gene expression [31].

References