title: An octamer element is required for the expression of the alpha H2B histone gene during the early development of the sea urchin.
abstract: Early (alpha) histone genes are one of several histone gene families in the sea urchin genome. They are expressed at high levels in blastula-stage embryos and are inactivated by the early gastrula stage. By microinjecting mutant early H2B genes into sea urchin zygotes and monitoring their transcriptional activity in blastula- and gastrula-stage embryos, we sought to identify the cis-regulatory elements responsible for this dramatic change in early H2B gene activity. We found that deletion of DNA 5' of -71 and 3' of +591 did not affect the timing or magnitude of early H2B gene expression. Neither was early H2B gene expression affected by the replacement of sequences downstream of -36 with the corresponding region of the L1 late H2B gene, expressed after the peak transcription of the early H2B gene. Further deletion of early H2B promoter sequences from -71 to -56, removing a conserved octamer element, resulted in near-complete inactivation of the early H2B gene in both blastula- and gastrula-stage embryos. Also inactivating early H2B gene expression were an internal deletion of the octamer element and a base substitution mutation that altered its sequence. This base substitution mutation also caused a parallel reduction in the ability of the octamer element to bind a factor present in nuclear extracts of sea urchin blastulae. These data strongly suggest that the proper expression of the early H2B gene in cleavage- and blastula-stage embryos depends on the octamer element and a factor with which it interacts.
authors.affiliation: Department of Biochemistry, University of Southern California, School of Medicine, Los Angeles 90033.
authors.forename: J
authors.initials: J
authors.lastname: Bell
authors.forename: B R
authors.initials: BR
authors.lastname: Char
authors.forename: R
authors.initials: R
authors.lastname: Maxson
mesh_terms: D000818:Animals; D001483:Base Sequence; D002872:Chromosome Deletion; D003001:Cloning, Molecular; D005775:Gastrula / Q000502:physiology; D005786:Gene Expression Regulation; D006657:Histones / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D015183:Restriction Mapping; D012617:Sea Urchins / Q000196:embryology* / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid
chemical_list: D006657:Histones; D009838:Oligodeoxyribonucleotides