[3H]UTP incorporation in permeabilized mouse L-cells is inhibited by antibodies directed against a structural nuclear...

Newly transcribed RNA is apparently attached to a nuclear structural framework whose main proteins are lamins A, C and B. Whether this attachment is fortuitous or has some functional importance was tested by measuring [3H]UTP incorporation into RNA of permeabilized mouse L-cells after incubation with antibodies against these polypeptides. Antibodies against only lamin B and not against lamins A, C inhibited low concentration alpha-amanitin-sensitive RNA transcription. Lamin B antibodies inhibited only in an assay system with whole nuclei and not in a soluble assay system. Anti-lamin B therefore does not block the actual transcriptional machinery, but rather seems to crosslink the structural framework on which transcription takes place in the intact nucleus, inhibiting dynamic changes essential to RNA synthesis.