No abstract

Multiple regulatory domains within the-100 region of the beta interferon (IFN-P) promoter control the inducible response of the IFN gene to virus infection. In this study, we demonstrate that the formation of NF-KB-specific complexes on the positive regulatory domain II (PRDII) precedes the onset of detectable IFN-I transcription in Sendai virus-infected cells. By using NF-KB subunit-specific antibodies, a temporal shift in the composition of NF-KB subunits in association with the PRDII domain is detected as a function of time after virus infection. Furthermore, a virus-induced degradation of IKBBa (MAD3) protein is observed between 2 and 8 h after infection; at later times, de novo synthesis of IKBa restores IKBC(to levels found in uninduced cells and correlates with the down regulation of IFN-0 transcription. In cotransfection experiments using various NF-KB subunit expression plasmids and two copies of PRDIIINF-KB linked to a chloramphenicol acetyltransferase reporter gene, we demonstrate that expression of p65, c-Rel, or p50 or combinations of p5O-p65 and p65-c-Rel differentially stimulated PRDII-dependent transcription. Coexpression of IK.Ba completely abrogated p65-, c-Rel-, or p65-p50-induced gene activity. When the entire IFN-4 promoter (-281 to +19) was used in coexpression studies, synergistic stimulation of IFN-f promoter activity was obtained when NF-KB subunits were coexpressed together with the IFN regulatory factor 1 (IRF-1) transcription factor. Overexpression of either IKB or the IRF-2 repressor was able to abrogate inducibility of the IFN-jI promoter. Thus, multiple regulatory events-including differential activation of DNA-binding NF-cB heterodimers, degradation of IKBa, synergistic interaction between IRF-1 and NF-KB, and decreased repression by IKB and IRF-2-are all required for the transcriptional activation of the IFN-, promoter.

No abstract

In summary, based on (a) their effects on DNA, RNA, protein synthesis and on the cell cycle, (b) their alkylating power and (c) their interactions with DNA, the 3-(2-chloroethyl)tetrazepinones appeared to kill tumor cells by a novel mechanism which may significantly differ from that of their 3-(2-chloroethyl)-tetrazinone counterpart, mitozolomide.