Antibodies specific to histone H1 inhibit in vitro transcription in isolated mammalian nuclei.

The issue of whether histone H1 is present in transcriptionally active chromatin has been approached by studying the effect specific anti-H1 antibodies have on in vitro transcription in isolated nuclei. To that end, the incorporation of radioactive RNA precursors into trichloroacetic acid-precipitable material was compared for control nuclei and nuclei that had been preincubated with specific anti-H1 antibody populations (whole sera, affinity-purified immunoglobulins and monovalent Fab fragments). The anti-H1 antibodies significantly and reproducibly inhibited the transcriptional activity in isolated nuclei. Experiments were also performed to exclude the possibility that the inhibition observed was due to some long-distance effect of the binding of the antibodies to chromatin. The results are interpreted as indicating that active gene chromatin does contain histone H1.