We demonstrated that MIF-1, identified initially as a binding activity that associated with the intron I element of the c-myc gene, consists of two polypeptides, the myc intron-binding peptide (MIBP1) and the major histocompatibility class II promoter-binding protein, RFX1. Using a polyclonal antiserum directed against either oligonucleotide affinity-purified MIBP1 or a peptide derived from RFX1, we showed that MIBP1 and RFX1 are distinct molecules that associate in vivo and are both present in DNA-protein complexes at the c-myc (MIF-1) and major histocompatibility complex class II (RFX1) binding sites. We have also found that MIBP1 and RFX1 bind to a regulatory site (termed EP) required for enhancer activity of hepatitis B virus. In addition, we have identified MIF-1-like sequences within regulatory regions of several other viral genes and have shown that MIBP1 binds to these sites in cytomegalovirus, Epstein-Barr virus, and polyomavirus. We have also demonstrated that the MIF-1 and EP elements can function as silencers in the hepatocarcinoma HepG2 and the cervical carcinoma HeLa cell lines. These findings indicate that MIBP1 and EP/RFX1 can associate in vivo and may regulate the expression of several distinct cellular and viral genes.The product of the c-myc oncogene has been implicated in diverse cellular processes, including cell proliferation, differentiation, and tumorigenesis. The observation that c-Myc can heterodimerize with other cellular proteins to transactivate gene expression in vitro has suggested that c-Myc may function to modulate genes involved in cell growth and differentiation pathways (3,4,14). The regulation of the c-myc gene involves a complex interplay of cis-and trans-acting elements, and several nuclear proteins that interact with regulatory sequences found in the 5Ј upstream and exon I untranslated regions of the c-myc gene have been identified (16,31). In addition, a 20-bp region of intron I was defined as a binding site for a phosphoprotein, initially designated MIF-1, and it was demonstrated that binding to this site was abolished by a point mutation present in the corresponding region of a translocated Burkitt's lymphoma c-myc gene (34,35). Adjacent binding sites in c-myc intron I were also identified and designated MIF-2 and MIF-3 (33), and somatic mutations found in Burkitt's lymphoma samples were shown to be frequently clustered within discrete domains that define these recognition sequences (33). These findings suggested that the mutations clustering in this region of the c-myc gene in Burkitt's lymphoma may be targeting specific regulatory elements for c-myc regulation, although direct evidence for this is lacking.It was recently demonstrated that the RFX1 protein, which binds to the X box of the major histocompatibility complex (MHC) class II genes, the methylated DNA-binding protein (MDBP), and the EP protein, which binds to the enhancer of hepatitis B virus (HBV), all represent the same DNA binding activity (29,36). The X-box sequence has been shown to play a role in regula...

The frequency ADH2-2 allele in the Moscow urban population and a correlation between the ADH2-2 allele, alcoholic dependence without cirrhosis, symptomatic alcoholic cirrhosis and status on hepatitis B and C infection have been studied. One hundred and twenty-three inhabitants of Moscow (50 healthy donors, 36 patients with alcoholic cirrhosis (subdivided into infected and uninfected by HBV and/or HCV) and 37 patients with alcoholic dependence) of a similar age/sex and drinking pattern have been analysed. The frequency of 41% for ADH2-2 allele is characteristic for an urban Moscow population. This value is intermediate between that found for Asian peoples and for Central and Western Europe. There is a negative correlation between the ADH2-2 allele and alcohol misuse (both alcoholic dependence and alcoholic cirrhosis). This correlation is expressed more in alcoholic dependence. In spite of the possession of the ADH2-2 allele (or genotype ADH2-1/2), alcohol misuse increases the risk of cirrhosis. At the same time, positive status for active hepatitis B, C or combined infection B + C (replication markers HBV-DNA or HCV-RNA) increases the risk for symptomatic alcoholic cirrhosis in alcohol abusing patients, independently of ADH2 genotype.

Supranucleosomal chromatin structure has been analysed by the use of histone H1 polymers crosslinked in nuclei and extended chromatin with bifunctional reagents methyl-4-mercaptobutyrimidate (MMB) and dimethyl suberimidate dihydrochloride. Almost pure H1 homopolymers were obtained in milligram amounts and examined for the distribution in molecular weights. The H1 homopolymer molecules both from nuclei and chromatin have been found to be integer multiples of an elementary structure (called "clisone") consisting of 12 histone H1 molecules. This finding strongly suggests that nucleosomal chains of chromatin are not uniform but rather organized as repeating oligonucleosomal units each consisting of 12 nucleosomes. Correlation between oligonucleosomal structures in nuclei and chromatin implies that a linearized nucleosomal chain retains the information on chromatin superstructure. The relation of the disclosed 12-nucleosome units to superbeads (nucleomeres) and other structures is discussed.

Expression of c‐myc proto oncogene is regulated by multiple mechanisms. Here, we report that the consensus of the regulatory region of interferondependent genes, GGAAAN1−3 GAAA, was found after computer search in the 5'‐terminal flank of human c‐myc gene in position (−76:−67). In vitro transcription of c‐myc gene fragments showed that the consensus region competes with oligonucleotide GGGAAAATGAAACT for binding to specific protein(s). This oligonucleotide was shown to bind selectively the interferon‐dependent positive transcription factor [1]. Transcription of c‐myc fragments lacking 5'‐terminal region up to positions −101 or +71 was initiated at two sites located in the first intron. These sites did not coincide with P1 in vivo RNA cap‐site. Binding of the protein factor(s) to the regulatory region of c‐myc gene −76:−67 blocked the in vitro transcription initiated in the first intron.

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