Phosphorylated Lamin A/C in the nuclear interior binds active enhancers associated with abnormal transcription in progeria

Abstract

LMNA encodes nuclear lamin A/C that tethers lamina-associated heterochromatin domains (LADs) to the nuclear periphery. Point mutations in LMNA cause degenerative disorders including the premature aging disorder Hutchinson-Gilford progeria, but the mechanisms are unknown. We report that Ser22-phosphorylated Lamin A/C (pS22-Lamin A/C) was localized to the interior of the nucleus in human fibroblasts throughout the cell cycle. pS22-Lamin A/C interacted with a specific subset of putative active enhancers, not LADs, primarily at locations co-bound by the transcriptional activator c-Jun. In progeria-patient fibroblasts, a subset of pS22-Lamin A/C-binding sites were lost whereas new pS22-Lamin A/C-binding sites emerged in normally quiescent loci. These new pS22-Lamin A/C-binding sites displayed increased histone acetylation and c-Jun binding, implying increased enhancer activity. The genes near these new binding sites, implicated in clinical components of progeria including carotid artery diseases, hypertension, and cardiomegaly, were upregulated in progeria. These results suggest that Lamin A/C regulates gene expression by direct enhancer binding in the nuclear interior. Disruption of the gene regulatory rather than LAD function of Lamin A/C presents a novel mechanism for disorders caused by LMNA mutations including progeria. HIGHLIGHTSO_LIpS22-Lamin A/C is present in the nuclear interior throughout interphase. C_LIO_LIpS22-Lamin A/C associates with active enhancers, not lamina-associated domains. C_LIO_LIpS22-Lamin A/C-genomic binding sites are co-bound by the transcriptional activator c-Jun. C_LIO_LINew pS22-Lamin A/C binding in progeria accompanies upregulation of disease-related genes. C_LI