Nonredundant and locus-specific gene repression functions of PRC1 paralog family members in human hematopoietic stem/progenitor cells.
The Polycomb group (PcG) protein BMI1 is a key factor in regulating hematopoietic stem cell (HSC) and leukemic stem cell self-renewal and functions in the context of the Polycomb repressive complex 1 (PRC1). In humans, each of the 5 subunits of PRC1 has paralog family members of which many reside in PRC1 complexes, likely in a mutually exclusive manner, pointing toward a previously unanticipated complexity of Polycomb-mediated silencing. We used an RNA interference screening approach to test the functionality of these paralogs in human hematopoiesis. Our data demonstrate a lack of redundancy between various paralog family members, suggestive of functional diversification between PcG proteins. By using an in vivo biotinylation tagging approach followed by liquid chromatography-tandem mass spectrometry to identify PcG interaction partners, we confirmed the existence of multiple specific PRC1 complexes. We find that CBX2 is a nonredundant CBX paralog vital for HSC and progenitor function that directly regulates the expression of the cyclin-dependent kinase inhibitor p21, independently of BMI1 that dominantly controls expression of the INK4A/ARF locus. Taken together, our data show that different PRC1 paralog family members have nonredundant and locus-specific gene regulatory activities that are essential for human hematopoiesis.
Department of Experimental Hematology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
Vincent
V
van den Boom
Marjan
M
Rozenveld-Geugien
Francesco
F
Bonardi
Donatella
D
Malanga
Djoke
D
van Gosliga
Anne Margriet
AM
Heijink
Giuseppe
G
Viglietto
Giovanni
G
Morrone
Fabrizia
F
Fusetti
Edo
E
Vellenga
Jan Jacob
JJ
Schuringa
D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D005260:Female; D005312:Fetal Blood / Q000166:cytology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D020868:Gene Silencing / Q000502:physiology; D056426:Genetic Loci / Q000235:genetics*; D006410:Hematopoiesis / Q000235:genetics; D006412:Hematopoietic Stem Cells / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D007231:Infant, Newborn; D005810:Multigene Family / Q000235:genetics / Q000502:physiology; D011247:Pregnancy; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D017385:Sequence Homology; D013379:Substrate Specificity / Q000235:genetics
D018797:Cell Cycle Proteins; C116662:PRC1 protein, human; D020033:Protein Isoforms; D012097:Repressor Proteins