The A- and B-type nuclear lamin networks: Microdomains involved in chromatin organization and transcription

Takeshi Shimi, Katrin Pfleghaar, Shin Ichiro Kojima, Chan Gi Pack, Irina Solovei, Anne E. Goldman, Stephen A. Adam, Dale K. Shumaker, Masataka Kinjo, Thomas Cremer, Robert D. Goldman

Research output: Contribution to journalArticlepeer-review

309 Scopus citations

Abstract

The nuclear lamins function in the regulation of replication, transcription, and epigenetic modifications of chromatin. However, the mechanisms responsible for these lamin functions are poorly understood. We demonstrate that A- and B-type lamins form separate, but interacting, stable meshworks in the lamina and have different mobilities in the nucleoplasm as determined by fluorescence correlation spectroscopy (FCS). Silencing lamin B1 (LB1) expression dramatically increases the lamina meshwork size and the mobility of nucleoplasmic lamin A (LA). The changes in lamina mesh size are coupled to the formation of LA/C-rich nuclear envelope blebs deficient in LB2. Comparative genomic hybridization (CGH) analyses of microdissected blebs, fluorescence in situ hybridization (FISH), and immunofluorescence localization of modified histones demonstrate that gene-rich euchromatin associates with the LA/C blebs. Enrichment of hyperphosphorylated RNA polymerase II (Pol II) and histone marks for active transcription suggest that blebs are transcriptionally active. However, in vivo labeling of RNA indicates that transcription is decreased, suggesting that the LA/C-rich microenvironment induces promoter proximal stalling of Pol II. We propose that different lamins are organized into separate, but interacting, microdomains and that LB1 is essential for their organization. Our evidence suggests that the organization and regulation of chromatin are influenced by interconnections between these lamin microdomains.

Original languageEnglish (US)
Pages (from-to)3409-3421
Number of pages13
JournalGenes and Development
Volume22
Issue number24
DOIs
StatePublished - Dec 15 2008

Keywords

  • Chromatin
  • Chromosome organization
  • Lamins
  • RNA polymerase II transcription

ASJC Scopus subject areas

  • Genetics
  • Developmental Biology

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