Cohesin is required for higher-order chromatin conformation at the imprinted IGF2-H19 locus.
Cohesin is a chromatin-associated protein complex that mediates sister chromatid cohesion by connecting replicated DNA molecules. Cohesin also has important roles in gene regulation, but the mechanistic basis of this function is poorly understood. In mammalian genomes, cohesin co-localizes with CCCTC binding factor (CTCF), a zinc finger protein implicated in multiple gene regulatory events. At the imprinted IGF2-H19 locus, CTCF plays an important role in organizing allele-specific higher-order chromatin conformation and functions as an enhancer blocking transcriptional insulator. Here we have used chromosome conformation capture (3C) assays and RNAi-mediated depletion of cohesin to address whether cohesin affects higher order chromatin conformation at the IGF2-H19 locus in human cells. Our data show that cohesin has a critical role in maintaining CTCF-mediated chromatin conformation at the locus and that disruption of this conformation coincides with changes in IGF2 expression. We show that the cohesin-dependent, higher-order chromatin conformation of the locus exists in both G1 and G2 phases of the cell cycle and is therefore independent of cohesin's function in sister chromatid cohesion. We propose that cohesin can mediate interactions between DNA molecules in cis to insulate genes through the formation of chromatin loops, analogous to the cohesin mediated interaction with sister chromatids in trans to establish cohesion.
Nativio
Raffaella
R
Department of Oncology, University of Cambridge, Cancer Research UK Cambridge Research Institute, Cambridge, United Kingdom.
Wendt
Kerstin S
KS
Ito
Yoko
Y
Huddleston
Joanna E
JE
Uribe-Lewis
Santiago
S
Woodfine
Kathryn
K
Krueger
Christel
C
Reik
Wolf
W
Peters
Jan-Michael
JM
Murrell
Adele
A
D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000502:physiology; D002478:Cells, Cultured; D002843:Chromatin / Q000737:chemistry / Q000648:ultrastructure*; D002868:Chromosomal Proteins, Non-Histone / Q000502:physiology; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics*; D056426:Genetic Loci; D018392:Genomic Imprinting; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D009690:Nucleic Acid Conformation; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated / Q000235:genetics*; D000097722:Cohesins
D018797:Cell Cycle Proteins; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D004247:DNA; D007335:Insulin-Like Growth Factor II; D062085:RNA, Long Noncoding; D022661:RNA, Untranslated; D000097722:Cohesins; C094335:H19 long non-coding RNA; C035170:IGF2 protein, human