MOLECULAR-MODELS OF SMALL PHOSPHORYLATED CHROMATIN PEPTIDES - STRUCTURE-FUNCTION RELATIONSHIP AND REGULATORY ACTIVITY ON IN-VITRO TRANSCRIPTION AND ON CELL-GROWTH AND DIFFERENTIATION

We previously reported the isolation of low molecular weight phosphory lated peptides from the chromatin of several tissues. The chromatin pe ptides show a regulatory activity on DNA in vitro transcription and on cell growth and differentiation. In this paper, we report a molecular model of the native peptides designed according to the stuctural info rmation obtained by means of biochemical and mass spectrometry analysi s: pyroGlu-Ala-Gly-Glu-Asp-Ser(P)-Asp-Glu-Glu-Asn. This or very simila r sequences are present in many transcription factors; on the basis of the structural model we presented and of related protein sequences, w e have synthesized the peptide pyroGlu-Asp-Asp-Ser-Asp-Glu-Glu-Asn. Th is peptide affects transcription rate in reconstituted systems in vitr o and in isolated nuclei; moreover, it inhibits the growth of HL60 cel ls with a parallel stimulus of differentiation.