Specific requirement of the chromatin modifier mSin3B in cell cycle exit and cellular differentiation

Abstract

The Sin3-histone deacetylase (HDAC) corepressor complex is conserved from yeast to humans. Mammals possess two highly related Sin3 proteins, mSin3A and mSin3B, which serve as scaffolds tethering HDAC enzymatic activity, and numerous sequence-specific transcription factors to enable local chromatin regulation at specific gene targets. Despite broad overlapping expression of mSin3A and mSin3B, mSin3A is cell-essential and vital for early embryonic development. Here, genetic disruption of mSin3B reveals a very different phenotype characterized by the survival of cultured cells and lethality at late stages of embryonic development with defective differentiation of multiple lineages-phenotypes that are strikingly reminiscent of those associated with loss of retinoblastoma family members or E2F transcriptional repressors. Additionally, we observe that, whereas mSin3B ؊/؊ cells cycle normally under standard growth conditions, they show an impaired ability to exit the cell cycle with limiting growth factors. Correspondingly, mSin3B interacts physically with the promoters of known E2F target genes, and its deficiency is associated with derepression of these gene targets in vivo. Together, these results reveal a critical role for mSin3B in the control of cell cycle exit and terminal differentiation in mammals and establish contrasting roles for the mSin3 proteins in the growth and development of specific lineages.E2F ͉ histone deacetylase ͉ knockout ͉ quiescence T he Sin3-histone deacetylase (HDAC) corepressor has been physically and functionally linked to diverse transcriptional complexes governing many physiological processes (1, 2). The two highly related mammalian Sin3 proteins, mSin3A and mSin3B, use their multiple interaction domains to direct chromatin-modifying activities to specific sites in the genome, most typically via sequence-specific transcription factors and their cognate binding elements. Class I HDACs, HDAC1 and HDAC2, are the principal enzymatic activities of the mSin3 complex. In addition, there are several other mSin3-associated proteins, including mSds3, p33 ING1 ,.mSin3A has been shown to be essential for early embryonic development and for the growth and survival of cultured cells that may relate to its requirement for the regulation of multiple transcriptional programs (7). Of relevance to the current study, mSin3B is expressed in cells deleted for mSin3A, suggesting that, despite their structural relatedness, mSin3B is not functionally equivalent to mSin3A. Both yeast and mammalian Sds3 are required for the maintenance of Sin3-associated HDAC enzymatic activity (3,8). Nullizygosity for mammalian Sds3 results in early embryonic lethality and engenders marked chromosome segregation defects due to a failure in pericentric heterochromatin formation (9). mSin3A-null fibroblasts exhibited normal karyotypes (7).In mammalian cell cycle, the G 0 /G 1 -to-S transition is a highly regulated event whose disruption represents a prerequisite for essentially all human cancers. This critical phase of the cell cy...

Common and specific roles of the related CDK inhibitors p27 and p57 revealed by a knock-in mouse model

“…Total RNA was extracted and purified from the intestine of E18.5 embryos and subjected to reverse transcription with a QuantiTect kit (Qiagen). The resulting cDNA was subjected to real-time PCR analysis as described previously (53), with 200 nM primers specific for E2F1 (54) or GAPDH (53). The abundance of E2F1 mRNA was normalized relative to that of GAPDH mRNA.…”

Senescence-associated SIN3B promotes inflammation and pancreatic cancer progression

“…We have recently demonstrated that mouse embryonic fibroblasts genetically inactivated for Sin3B are refractory to quiescence as well as oncogene-induced senescence (33)(34)(35). In addition, SIN3B levels are significantly upregulated in preneoplastic senescent lesions in a mouse model of PDAC (34).…”

“…Using this approach, we demonstrate here that the inactivation of Sin3B in the pancreas prevents oncogenic KRAS-induced senescence, correlating with a defect in the proinflammatory phenotype, ultimately resulting in delayed pancreatic cancer progression. tional allele were first crossed with transgenic mice expressing the Cre recombinase under the control of the pancreas-specific p48 promoter (35,36). Sin3B flox/+ p48-Cre + and Sin3B flox/-p48-Cre + animals (hereafter referred to as Sin3B p+/-and Sin3B p-/-) were born at the expected ratio (data not shown).…”

“…Sin3B p+/-animals were used as controls, as heterozygote animals are phenotypically indistinguishable from Sin3B +/+ animals through 16 months of age (data not shown and ref. 35). Similar to the control littermates, Sin3B p-/-animals exhibited no gross abnormalities up to 1 year of age and presented normal pancreatic morphology (Supplemental Figure 1A and data not shown; supplemental material available online with this article; doi:10.1172/JCI72619DS1).…”

Role of Signaling Pathways and Epigenetic Factors in Lineage Determination During Human Embryonic Stem Cell Differentiation

“…The ICM derived from these embryos shows severely retarded proliferation ex vivo [168]. Sin3b null embryos show defects in erythrocyte and granulocyte maturation and in skeletal development [170]. The Class III HDACs, known as Sirtuins (SirTs), are also implicated during differentiation and mammalian development [171].…”