Research Article 239 Nuclear Titin interacts with A- and B-type lamins in vitro and in vivo Michael S. Zastrow1,*, Denise B. Flaherty2‡, Guy M. Benian2 and Katherine L. Wilson1,§ 1Department of Cell Biology, The Johns Hopkins University School of Medicine, 725 N. Wolfe St, Baltimore, MD 21205, USA 2Department of Pathology, Emory University, Whitehead Biomedical Research Building, Atlanta, GA 30332, USA *Present address: Department of Developmental Biology, Stanford University School of Medicine, Beckman Center, B300, 279 Campus Drive, Stanford, CA 94305, USA ‡Department of Biology, Eckerd College, SHB 105, 4200 54th Ave, St Petersburg, FL 33711, USA §Author for correspondence (e-mail:
[email protected]) Accepted 4 October 2005 Journal of Cell Science 119, 239-249 Published by The Company of Biologists 2006 doi:10.1242/jcs.02728 Summary Lamins form structural filaments in the nucleus. Mutations lamin-downregulated [lmn-1(RNAi)] embryos, Ce-titin was in A-type lamins cause muscular dystrophy, undetectable at the nuclear envelope suggesting its cardiomyopathy and other diseases, including progeroid localization or stability requires Ce-lamin. In human cells syndromes. To identify new binding partners for lamin A, (HeLa), antibodies against the titin-specific domain M-is6 we carried out a two-hybrid screen with a human skeletal- gave both diffuse and punctate intranuclear staining by muscle cDNA library, using the Ig-fold domain of lamin A indirect immunofluorescence, and recognized at least three as bait. The C-terminal region of titin was recovered twice. bands larger than 1 MDa in immunoblots of isolated HeLa Previous investigators showed that nuclear isoforms of titin nuclei.