Specific Binding of High-Mobility-Group I (HMGI) Protein and Histone H1 to the Upstream AT-Rich Region of the Murine Beta Interferon Promoter: HMGI Protein Acts as a Potential Antirepressor of the Promoter

Abstract

The high-mobility-group I (HMGI) protein is a nonhistone component of active chromatin. In this work, we demonstrate that HMGI protein specifically binds to the AT-rich region of the murine beta interferon (IFN-␤) promoter localized upstream of the murine virus-responsive element (VRE). Contrary to what has been described for the human promoter, HMGI protein did not specifically bind to the VRE of the murine IFN-␤ promoter. Stably transfected promoters carrying mutations on this HMGI binding site displayed delayed virusinduced kinetics of transcription. When integrated into chromatin, the mutated promoter remained repressed and never reached normal transcriptional activity. Such a phenomenon was not observed with transiently transfected promoters upon which chromatin was only partially reconstituted. Using UV footprinting, we show that the upstream AT-rich sequences of the murine IFN-␤ promoter constitute a preferential binding region for histone H1. Transfection with a plasmid carrying scaffold attachment regions as well as incubation with distamycin led to the derepression of the IFN-␤ promoter stably integrated into chromatin. In vitro, HMGI protein was able to displace histone H1 from the upstream AT-rich region of the wild-type promoter but not from the promoter carrying mutations on the upstream high-affinity HMGI binding site. Our results suggest that the binding of histone H1 to the upstream AT-rich region of the promoter might be partly responsible for the constitutive repression of the promoter. The displacement by HMGI protein of histone H1 could help to convert the IFN-␤ promoter from a repressed to an active state.

Effects of Scaffold/Matrix Alteration on Centromeric Function and Gene Expression

“…For example, treatment with this drug has resulted in the repression of the mouse mammary tumor virus (MMTV) and ␤-interferon (IFN-␤) gene promoters (50,69). However, at 75 g/ml DST, we have detected no significant alteration to the expression activities of any of the genes residing at the 10q25 neocentromere.…”

A Repressor-Antirepressor Pair Links Two Loci Controlling Light-induced Carotenogenesis in Myxococcus xanthus

“…Distinct mechanisms for how the antirepressor antagonizes repressor activity include the following: (a) direct protein-protein association without any DNA binding by the antirepressor (42)(43)(44)(45); (b) exclusion of the repressor by DNA binding of the antirepressor (46); and (c) proteolysis of the repressor promoted by the antirepressor (47). Our data have revealed that the monomeric CarS, which does not itself bind DNA, physically interacts with CarA.…”

Transcription Factor YY1 Binds to the Murine Beta Interferon Promoter and Regulates Its Transcriptional Capacity with a Dual Activator/Repressor Role

“…Plasmid constructions were carried out by double PCR as previously described (3) by using plasmid pBLCAT3-muIFN-␤ wt330 as a template. This plasmid carries the wild-type murine IFN-␤ (muIFN-␤) promoter fragment from Ϫ330 to ϩ20 cloned in front of the CAT reporter gene of plasmid pBLCAT3 (3). For primers, we used the corresponding mutated oligonucleotides described in Table 1 as well as primer Ϫ40 (5Ј-GTTTTCCCAGTCACGAC-3Ј) and primer CAT (5Ј-CCATTTTAGCTTCCTTAG-3Ј).…”

“…A strong HMGI binding site is present in the muIFN-␤ promoter next to the YY1-binding site present at position Ϫ122, and disruption of this site has been determined to lead to a reduced promoter activity (3). In order to test the eventual effect of the mutation in strain mut122 on the DNA-binding capacity of protein HMGI to the IFN-␤ promoter, gel retardation experiments were carried out with wt330, mut90, and mut122 promoters (from position Ϫ330 to ϩ20) and recombinant HMGI protein.…”