Dev Biol 1992 Apr 01;1502:363-71. doi: 10.1016/0012-1606(92)90248-f.

An octamer element is required for the expression of the alpha H2B histone gene during the early development of the sea urchin.

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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.

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Genes referenced: LOC100887844