FIG. 1.

Transcription is repressed in whole-cell extracts prepared from mitotic cells in culture. (A) Histone H1 kinase activity of asynchronous (A) and mitotic (M) cell extracts. Equivalent amounts of extract protein were used as a source of kinase, along with histone H1 and [γ-³²P]ATP, as described in Materials and Methods. Radiolabeled histone H1 was visualized by autoradiography of an SDS-polyacrylamide gel. The positions of molecular mass markers (denoted in kilodaltons) are indicated. (B) Transcription of the human CMV MIEP (CMV) and the HIV-1 promoter (HIV), both linked to guanineless cassettes (G−), was monitored, using equivalent amounts of extract protein from asynchronous (A) or mitotic (M) cells, as described in Materials and Methods. The gel autoradiogram is shown.