The Molecular Functions Of Mga In Polycomb Repressive Complex 1.6

Polycomb group(PcG)proteins are epigenetic modifiers involved in controlling gene repression.They are organized in multiprotein complexes,such as Polycomb Repressive Complexes I and II(PRC1 and PRC2).The composition of PRC1 in mammals is very compicated and dynamic,and PRC1 can be divided into six classes(PRC1.1-1.6)based on which PCGF(PCGF1-6)it contains.During the preliminary work about protein interaction in PRC1,they find a new protein,Mga(MAX gene associated).It is a dual-specificity transcription factor and an important component of PRC1.6.Due to its large size(3042 aa)and potential technical difficulties,it has been lacking of study and literature report about its expression and regulation,interacting partners and key roles in PRC1.6.In this study,we mainly focused on the characterization of Mga in order to elucidate the molecular functions of PRC1.6 complex.Methods:(1)We carried out BiFC and Ni-pulldown assay to identify the detailed region(s)within RING1 B interacting with Mga 535-640 aa in vivo and vitro.(2)We tested the expression of Mga splicing variants in mouse tissues through real-time PCR and established the tissue expression spectrogram of Mga transcription splicing variants.(3)Previous experiments through microarray got upregulated genes specifically invloved in spermatogenesis upon Mga KD in mouse embryonic stem cells.We analyzed the upregulated genes in stem cells after Mga KD with other published dates of Pcgf6,L3mbtl2,Ring1 b in PRC1.6 through bioinformatics approaches,such as Ingenuity Pathway Anaylsis(IPA),Gene Ontology,PANTHER Classifiation System to find the common characteristics.Results and conclusions:(1)The fragment of RIN1 B which interacts with Mga(535-640)is its C terminal.(2)The Mga splicing variant Isoform A express highest in mouse tissues we tested.Other splicing variants more or less is express in this tissues.Isoform A and several other Isoforms are higher expressed in testis than other tissues saying that Mga may have an important role in testis.(3)Components of PRC1.6,Mga,Pcgf6,L3mblt2 and RING1 B commanly repress a series of genes associated with spermatogenesis and miosis in stem cells.