TRANSCRIPTIONAL DOWN-REGULATION OF TUMOR-NECROSIS-FACTOR-ALPHA GENE-EXPRESSION BY A SYNTHETIC PEPTIDE HOMOLOGOUS TO RETROVIRAL ENVELOPE PROTEIN

We have previously shown that a synthetic peptide (CKS-17) homologous to retroviral envelope protein suppresses the accumulation of superant igen staphylococcal enterotoxin-induced TNF-alpha mRNA in human PBMC a nd in highly purified human monocytes. The present study was designed to examine the underlying mechanism(s) by which CKS-17 down-regulates the TNF-alpha mRNA expression using a human acute monocytic leukemia c ell line THP-1 stimulated with the superantigen staphylococcal enterot oxin E. A cyclooxygenase inhibitor indomethacin does not reverse the i nhibition of TNF-alpha mRNA expression by CKS-17, suggesting that pros taglandins are not responsible for the suppressive action of CKS-17. T he inhibitory effect of CKS-17 is, however, significantly blocked by a protein synthesis inhibitor cycloheximide, indicating that CKS-17 req uires de novo protein synthesis to induce the suppressive activity. Th e mRNA stability assays using actinomycin D show that CKS-17 does not decrease the TNF-alpha mRNA stability. Nuclear run-on transcription as says further reveal that CKS-17 suppresses the TNF-alpha mRNA transcri ption rate. Taken together, these results suggest that the synthetic r etroviral peptide CKS-17 down-regulates TNF-alpha mRNA expression thro ugh inhibition of transcriptional activation of the TNF-alpha gene, wh ich requires de novo synthesis of a transcriptional repressor protein( s).