p53에 의한 HIV-1 Tat 활성억제와 ds-RNA-dependent Protein Kinase (PKR) 관련 가능성 연구

p53-mediated HIV-1 Tat Suppression is Likely to be Associated with duble-stranded RNA-dependent Protein Kinase, PKR

HIV-1 Tat, a strong transactivator, is essential for the HIV-1 replication and AIDS progression. The Tat function is markedly inhibited by human p53 anti-oncogene. However, the detail mechanism has not yet been clearly revealed. In our previous report, we have addressed that p53 is unlikely to interact directly with HIV-1 Tat. In the consecutive experiments, Tat-phosphorylation was found to increase in proportional to the amounts of transfected p53. This work was initiated to identify the signaling factor that is involved in the p53-mediated Tat suppression. Several protein kinases were tested for the phosphorylation of Tat, and we found that PKR is likely to be involved in the p53-mediated Tat suppression. PKR was co-immunoprecipitated by anti-Tat antibody in the Tat-expressing Jurkat cell lysates only when the cells were transfected by p53, indicating that PKR-Tat interaction depends on the p53 activity. The interaction seems to result in PKR-mediated Tat-phosphorylation. Tat function was not blocked by p53 when co-transfected trasiently with antisense-PKR. We have generated PKR-knock out Jurkat cell clone. The PKR defective Jurkat cells didn't show the p53-mediated Tat suppression. These data indicate that p53-mediated Tat suppression is strongly associated with PKR. PKR-mediated Tat phosphorylation experiments are now under investigation by kinase assay and co-immunoprecipitation in the presence or absence of p53.