Visualization by BiFC of different C/EBPb; dimers and their interaction with HP1a; reveals a differential subnuclear distribution of complexes in living cells

SEBASTIÁN SUSPERREGUY; LUCIANA PAOLA PRENDES; MARÍA A. DESBATS; NANCY L. CHARÓ; KAREN BROWN; ORMOND A. MACDOUGALD; TOM KERPPOLA; JESSICA SCHWARTZ; GRACIELA PIWIEN PILLIPUK

EXPERIMENTAL CELL RESEARCH

ELSEVIER INC

Año: 2011 vol. 317 p. 706 - 723

0014-4827

How the co-ordinated events of gene activation and silencing during cellular differentiation areinfluenced by spatial organization of the cell nucleus is still poorly understood. Little is knownabout the molecular mechanisms controlling subnuclear distribution of transcription factors, andtheir interplay with nuclear proteins that shape chromatin structure. Here we show that C/EBPβnot only associates with pericentromeric heterochromatin but also interacts with thenucleoskeleton upon induction of adipocyte differentiation of 3T3-L1 cells. Different C/EBPβdimers localize in different nuclear domains. Using BiFC in living cells, we show that LAP (LiverActivating Protein) homodimers localize in euchromatin and heterochromatin. In contrast, LIP(Liver Inhibitory Protein) homodimers localize exclusively in heterochromatin. Importantly, theirdifferential subnuclear distribution mirrors the site for interaction with HP1α. HP1α inhibits LAPtranscriptional capacity and occupies the promoter of the C/EBPβ-dependent gene c/ebpα in 3T3-L1 preadipocytes. When adipogenesis is induced, HP1α binding decreases from c/ebpα promoter,allowing transcription. Thus, the equilibrium among different pools of C/EBPβ associated withchromatin or nucleoskeleton, and dynamic changes in their interaction with HP1α, play key roles inthe regulation of C/EBP target genes during adipogenesis.