Boris A. Leibovitch

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Genes normally resident in euchromatic domains are silenced when packaged into heterochromatin, as exemplified in Drosophila melanogaster by position effect variegation (PEV). Loss-of-function mutations resulting in suppression of PEV have identified critical components of heterochromatin, including proteins HP1, HP2, and histone H3 lysine 9(More)
MMSET, identified by its fusion to the IgH locus in t(4;14)-associated multiple myeloma, possesses domains found within chromatin regulators, including the SET domain. MMSET protein is overexpressed and highly associated with chromatin in myeloma cell lines carrying t(4;14). MMSET possesses methyltransferase activity for core histone H3 lysine 4 and histone(More)
The upstream regulatory region of the Drosophila melanogaster hsp26 gene includes two DNase I-hypersensitive sites (DH sites) that encompass the critical heat shock elements. This chromatin structure is required for heat shock-inducible expression and depends on two (CT)n*(GA)n elements bound by GAGA factor. To determine whether GAGA factor alone is(More)
Preparations of polytene chromosomes of D. melanogaster fixed with acetic acid have been used as templates for RNA synthesis by E. coli RNA polymerase complete or core enzymes in the presence of 3H-nucleoside triphosphates. Radioautographic experiments showed that on a single X-chromosome from male larvae twice as much RNA is synthesized as on each of the(More)
We have determined the number of histone structural genes in D. melanogaster heterozygotes for two different deficiencies of a histone locus in the 2d chromosome. the results indicate a possibility of histone genes increasing in number in the case of their deficiency through magnification and compensation, as has been shown for rRNA genes by other authors.
We generated a transgenic (Tg)-mouse model expressing a dominant negative-(DN)-RARα, (RARαG303E) under adipocytes-specific promoter to explore the paracrine role of adipocyte retinoic acid receptors (RARs) in mammary morphogenesis. Transgenic adipocytes had reduced level of RARα, β and γ, which coincided with a severely underdeveloped pubertal and mature(More)
The deficiency of the 38B-40 region containing histone genes in one of the 2nd chromosomes of D. melanogaster triploid intersexes increases the template activity of X-chromosomes both in vivo and in vitro without noticeably affecting autosome activity. This deficiency in the heterozygous state inhibits the variegated position effect of the white gene in the(More)
A comparative radioautographic study of the RNA precursors incorporation on polytene chromosomes of Drosophila in vivo in the cells of salivary glands, and in vitro during incubation of E. coli RNA polymerase on slides with fixed chromosomes was performed. — The pattern of in vivo 3H-uridine incorporation on different sections of the chromosomes drastically(More)
It is increasingly clear that the packaging of DNA in nucleosome arrays serves not only to constrain the genome within the nucleus, but also to encode information concerning the activity state of the gene. Packaging limits the accessibility of many regulatory DNA sequence elements and is functionally significant in the control of transcription, replication,(More)