Biomedical subjects
D Adrian
Publications and source records attributed to D Adrian.
Diminished production of human immunodeficiency virus type 1 in astrocytes results from inefficient translation of gag, env, and nef mRNAs despite efficient expression of Tat and Rev.
Astrocytes infected with human immunodeficiency virus type 1 (HIV-1) produce only minimal quantities of virus. The molecular events that limit acute-phase HIV-1 infection of astrocytes were examined after inducing acute-phase replication by transfection with the pNL4-3 proviral plasmid. The levels of HIV-1 mRNA were similarly high in both astrocytes and HeLa cells, but astrocytes produced approximately 50-fold less supernatant p24 than HeLa cells. We found that diminished HIV-1 production in astrocytes resulted from inefficient translation of gag, env, and nef mRNAs that were efficiently transported to the cytoplasm. Tat- or Rev-dependent reporter constructs showed no defect in Tat or Rev function in astrocytes compared with HeLa cells. HIV-1 mRNAs were correctly spliced, but only Rev and Tat proteins were efficiently translated from their native mRNAs. Pulse-chase labelling and immunoblot experiments revealed no defect in protein processing, but levels of Gag, Env, or Nef protein expressed were dramatically reduced in astrocytes compared to HeLa cells. These results demonstrate that inefficient translation of HIV-1 structural proteins underlies the restricted infection of astrocytes. The efficient expression of functional Tat and Rev by astrocytes may contribute to HIV-1 neuropathogenesis.
AZT induces high frequency, rapid amplification of centromeric DNA.
The reverse transcriptase inhibitor 3'-azido-deoxythymidine (AZT) has previously been shown to be incorporated into specific regions near the telomeres and centromeres of Chinese hamster ovary cell chromosomes. Our investigation of the effects of AZT on chromosome stability has led to the discovery of a high frequency amplification of telomere-like centromeric DNA. The amplified structures, when analyzed cytogenetically, appear as tandem arrays of tightly clustered blocks of centromeric repeats containing telomeric sequences (TTAGGG)n. There were 5-13 blocks of amplified DNA per structure. These structures form rapidly within one or two cell cycles and can be observed with an incidence as high as 2%. Because the amplification was so rapid, we tested whether the amplification structures could be the result of aberrant overreplication by analyzing BrdU incorporation. Our results indicate that the amplified DNA does not undergo abnormal replication during its formation, but appears to form from existing centromeric regions. We propose a model that involves the excision of multiple centromeric DNA regions from other chromosomes and their relocalization to a new site.
Expression of CD59, a regulator of the membrane attack complex of complement, on human astrocytes.
The present study demonstrates that human astrocytes synthesize and express CD59, a regulator of the membrane attack complex of complement. This was shown by flow cytometry following staining of astrocytes with MAb to CD59, and Western blotting of astrocyte lysates, which revealed the characteristic 18-23,000 M(r) band of CD59. Synthesis of CD59 by astrocytes was confirmed by detection of CD59 specific mRNA by polymerase chain reaction. A low level of C3 deposition occurred on astrocytes following exposure to autologous serum. CD59 may prevent subsequent damage from C5b-9 and protect astrocytes during inflammatory and infectious disorders of the nervous system.