Evidence for regulation of transcription and replication of the human neurotropic virus JCV genome by the human S(mu)bp-2 protein in glial cells.
Glial factor 1 (GF-1) is a partial cDNA isolated from a human brain cDNA library which encodes a truncated protein with binding ability to the B-regulatory domain of the human neurotropic virus, JCV. GF-1 exhibits sequence homology to the central region of the newly identified human DNA-binding protein S(mu)bp-2. GF-1 appears to be a partial cDNA for human S(mu)bp-2 based on its sequence homology to S(mu)bp-2 and their chromosomal co-localization. In this report, we have employed transfection assay and have compared the ability of GF-1 and its full-length form, S(mu)bp-2, on regulating the activity of JCV promoters in glial cells. Our results demonstrate that, unlike GF-1 which stimulates JCV early promoter in glial cells, overexpression of S(mu)bp-2 exhibits no drastic effect on the transcription of the viral early promoter. The activity of the viral late promoter was noticeably increased by both GF-1 and S(mu)bp-2, although the level of induction by GF-1 was consistently higher than that detected by S(mu)bp-2. Use of deletion constructs in co-transfection assay revealed that the B-domain of the JCV promoter is required for transcriptional activation by GF-1 and S(mu)bp-2. Expression of GF-1 and S(mu)bp-2 in glial cells increased the induced level of JCV late gene transcription by the viral early protein, T-antigen. Examination of the viral DNA replication by DpnI assay indicated that, unlike GF-1, S(mu)bp-2 has the ability to decrease the level of JCV DNA replication in glial cells. These observations suggest that the N-terminal portion of S(mu)bp-2 which encompasses several helicase motifs and/or its C-terminus, both of which are missing in GF-1, may confer differential effects on viral gene transcription and replication. The biological importance of our findings in regulation of the JCV lytic cycle in glial cells is discussed.
Chen
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NN
Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Kerr
D
D
Chang
C F
CF
Honjo
T
T
Khalili
K
K
D000957:Antigens, Viral, Tumor / Q000096:biosynthesis; D015152:Blotting, Northern; D002478:Cells, Cultured; D002874:Chromosome Mapping; D018076:DNA, Complementary / Q000235:genetics; D004279:DNA, Viral / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D015723:Gene Library; D017930:Genes, Reporter; D016679:Genome, Viral; D006801:Humans; D007577:JC Virus / Q000235:genetics* / Q000254:growth & development; D009457:Neuroglia / Q000166:cytology / Q000821:virology*; D030361:Papillomavirus Infections / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology; D014158:Transcription, Genetic; D014162:Transfection
D000957:Antigens, Viral, Tumor; D018076:DNA, Complementary; D004279:DNA, Viral; D004268:DNA-Binding Proteins; C489892:IGHMBP2 protein, human; D014157:Transcription Factors; C020102:endodeoxyribonuclease DpnI; D015252:Deoxyribonucleases, Type II Site-Specific