The HIV-1 transactivator protein Tat is a potent inducer of the human DNA repair enzyme beta-polymerase.
OBJECTIVE
This study examines the effects of the HIV-1 regulatory proteins, Tat and Rev, on the expression of the DNA polymerase beta (beta-pol) gene, which encodes a key protein in the DNA base-excision repair pathway. The rationale for these experiments is to examine the potential involvement of base-excision repair protein deregulation in HIV-1-related lymphomas.


METHODS
Expression of beta-pol mRNA was examined in AIDS-related lymphomas and non-AIDS-related lymphomas and as a function of HIV-1 infection of B cells in culture. The effect of Tat or Rev over-expression on beta-pol promoter expression was tested by transient co-transfection assays with a beta-pol promoter reporter plasmid and a Tat or Rev over-expression plasmid.


METHODS
Northern blot analysis was used to quantitate beta-pol expression in lymphoma and cells. Raji cells were co-transfected with a chloramphenicol acetyltransferase (CAT) reporter plasmid and a plasmid over-expressing Tat or Rev. CAT activity was measured in transfected cells.


RESULTS
beta-Pol mRNA was > 10-fold higher in AIDS-related than in non-AIDS B-lineage lymphomas. beta-Pol expression was up-regulated in a B-cell line upon infection with HIV-1, and increased in Raji cells upon recombinant expression of the Tat gene. The beta-pol promoter was transactivated (fourfold induction) by Tat, but not by Rev. Tat-dependent transactivation required a binding site for the transcription factor Sp1 in the beta-pol promoter.


CONCLUSIONS
These results suggest that HIV-1 Tat can interact with cellular transcription factors to increase the steady-state level of beta-pol in B cells. Tat-mediated induction of beta-pol may alter DNA stability in AIDS-related lymphomas.
Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina, USA.
D K
DK
Srivastava
C L
CL
Tendler
D
D
Milani
M A
MA
English
J D
JD
Licht
S H
SH
Wilson
D000818:Animals; D001483:Base Sequence; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D019951:DNA Polymerase beta / Q000096:biosynthesis / Q000235:genetics*; D004790:Enzyme Induction; D015967:Gene Expression Regulation, Viral; D015694:Gene Products, rev / Q000494:pharmacology; D015696:Gene Products, tat / Q000494:pharmacology*; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D016483:Lymphoma, AIDS-Related / Q000235:genetics* / Q000378:metabolism; D016393:Lymphoma, B-Cell / Q000235:genetics; D008969:Molecular Sequence Data; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D054321:rev Gene Products, Human Immunodeficiency Virus; D054322:tat Gene Products, Human Immunodeficiency Virus
D015694:Gene Products, rev; D015696:Gene Products, tat; D012333:RNA, Messenger; D054321:rev Gene Products, Human Immunodeficiency Virus; D054322:tat Gene Products, Human Immunodeficiency Virus; D015500:Chloramphenicol O-Acetyltransferase; D019951:DNA Polymerase beta