Isolation of transcriptionally active chromatin from mammalian nucleoli.

Abstract

Nucleoli isolated from HeLa cells [human cervical carcinoma cells] are functionally active but contain large amounts of RNA and proteins (RNA/DNA ratio 1:1; protein/DNA ratio 7:1). A DNA-protein complex that has the characteristics of nucleolar chromatin (RNA/DNA ratio < 0.05:1; protein/DNA ratio 1.7:1) was isolated from the nucleolus. This nucleolar chromatin has most of the transcriptional activity of the intact nucleolus and, as assayed by circular dichroism and dye binding, has largely preserved its structure. The isolation of a transcriptionally active fragment of chromatin, which constitutes only a small part of the total genome and codes for only 1 recognizable product, offers several advantages for the study of chromatin structure and function.