Two Heat-Resistant, Low Molecular Weight Proteins from Escherichia coli That Stimulate DNA-Directed RNA Synthesis

AUTOR(ES)

Cukier-Kahn, Regine

RESUMO

Two heat-stable protein factors, designated as H1 and H2, have been purified from a DNA-protamine sulfate complex obtained in an early step in the preparation of E. coli RNA polymerase. Gel electrophoresis under denaturing conditions indicates that H1 and H2 behave as pure entities, with molecular weights below 10,000. Their purity is confirmed by aminoacid composition data, and in the case of H1, by immunological assays. H1 and H2 both strongly stimulate transcription of DNA from bacteriophages λ and ϕ80 by the E. coli polymerase holoenzyme; no effect was observed with single-stranded templates. That the amount of H1 required for maximal stimulation is proportional to the amount of DNA present in the assay, and that both H1 and H2 strongly bind to native DNA in a synergestic fashion, suggests that these low molecular weight factors stimulate RNA synthesis by modifying the properties of the DNA template.

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