RESEARCH ARTICLE 513 α-Skeletal actin induces a subset of muscle genes independently of muscle differentiation and withdrawal from the cell cycle Peter W. Gunning1,3,4, Vicki Ferguson1,3, Karen J. Brennan2,* and Edna C. Hardeman2,‡ 1Cell Biology Unit and 2Muscle Development Unit, Children’s Medical Research Institute, Locked Bag 23, Wentworthville, NSW, 2145, Australia 3Oncology Research Unit, The New Children’s Hospital, PO Box 3515, Parramatta, NSW, 2124, Australia 4Department of Paediatrics and Child Health, University of Sydney, Sydney, NSW 2006, Australia *Present address: EMBL Heidelberg, Meyerhofstraße 1, Postfach 102209, D-69012 Heidelberg, Germany ‡Author for correspondence (e-mail:
[email protected]) Accepted 14 November 2000 Journal of Cell Science 114, 513-524 © The Company of Biologists Ltd SUMMARY Muscle differentiation is characterized by the induction of characteristic of muscle differentiation were induced. genes encoding contractile structural proteins and the Stable transfectants displayed a substantial reduction repression of nonmuscle isoforms from these gene families. in cell surface area and in the levels of nonmuscle We have examined the importance of this regulated order tropomyosins and β-actin, consistent with a relationship of gene expression by expressing the two sarcomeric muscle between the composition of the actin cytoskeleton and cell actins characteristic of the differentiated state, i.e. α- surface area. The transfectants displayed normal cell cycle skeletal and α-cardiac actin, in C2 mouse myoblasts. progression. We propose that α-skeletal actin can activate Precocious accumulation of transcripts and proteins for a regulatory pathway linking a subset of muscle genes that a group of differentiation-specific genes was elicited by operates independently of normal differentiation and α-skeletal actin only: four muscle tropomyosins, two withdrawal from the cell cycle.