Developmental and tissue-specific regulation of a novel transcription factor of the sea urchin.

Abstract

We have identified a novel transcription factor that interacts with the promoter of four tissue-specific late histone H2A-2 and H2B-2 genes of the sea urchin by DNase I footprint, mobility shift, and methylation interference analyses. The binding site for this factor is required for efficient transcription of the H2B-2.1 gene both in vitro in nuclear extracts of gastrula embryos and in vivo in microinjected sea urchin embryos. This factor binds with equal affinity to the recognition sequences of all four histone genes in cross-competition assays. Moreover, the binding site of the H2B-2.2 promoter can functionally substitute for that of the H2B-2.1 gene in in vivo expression experiments. Nevertheless, all four binding sites share little sequence homology with each other. This transcription factor increases in abundance during embryogenesis and has been detected in the adult sea urchin only in the tube feet, where the late H2A-2 and H2B-2 genes are expressed specifically. Therefore, we refer to this factor as tissue-specific activator protein (TSAP). The close correlation between the presence of TSAP and the expression pattern of the late H2A-2 and H2B-2 genes suggests that this transcription factor is directly responsible for the developmental and tissue-specific regulation of these genes.

A novel B-cell lineage-specific transcription factor present at early but not late stages of differentiation.

“…This complex is clearly specific, as unrelated pUC18 plasmid DNA starts to compete only at high DNA concentrations. Therefore, BSAP appears to recognize all four binding sites with equal affinity, as does the sea urchin TSAP (Barberis et al 1989).…”

“…Using the electrophoretic mobility-shift assay (Fried and Crothers 1981;Garner and Rezvin 1981), we have screened nuclear extracts of different murine and human cell lines for a DNA-binding activity homologous to the tissue-specific transcription factor TSAP of the sea urchin (Barberis et al 1989). The only cell line that scored positive in this initial screen was the human B-cell line BJA-B.…”

“…(A)Electrophoretic mobilityshift analysis. End-labeled oligonucleotides containing the TSAP-binding sites of the four late H2A-2 and H2B-2 genes (Barberis et al 1989) were incubated in nuclear extracts of sea urchin gastrula embryos and the human lymphoblastoid cell line BJA-B, followed by separation of the protein-DNA complexes on a native 4% polyacrylamide gel, as described in Materials and methods. B1 and B2 denote the two specific complexes of the sea urchin TSAP activity, and F indicates the position of free DNA.…”

“…Known recognition sequences of the sea urchin transcription factor TSAP. The promoter sequences of the four late histone H2A-2 and H2B-2 genes, protected by TSAP from DNase I digestion, are shown together with the deduced consensus sequence (see Barberis et al 1989). The only strictly invariant position {C) is highlighted by boldface type.…”

“…We have previously characterized a tissue-specific activator protein (TSAP) of the sea urchin, which is, at least in part, responsible for the developmental and tissue-specific regulation of two nonallelic pairs of late histone H2A-2 and H2B-2 genes (Barberis et al 1989). The four TSAP-binding sites of these genes are shown together with their deduced consensus sequence in Figure 1.…”