PubMed:12759432 JSONTXT

{"project":"2015-BEL-Sample","denotations":[{"id":"T1","span":{"begin":1326,"end":1464},"obj":"complex(p(MGI:Yy1),p(MGI:Rb1)) decreases tscript(p(MGI:Yy1))"}],"text":"Yin Yang 1 is a lipopolysaccharide-inducible activator of the murine 3' Igh enhancer, hs3.\nThe 3' Igh enhancers, DNase I hypersensitive site (hs) 3B and/or hs4, are required for germline transcription, and hence, class switch recombination for multiple isotypes. A number of hs3-binding transcription factors have been identified by EMSA, including octamer and NF-kappa B family members, and Pax5. We have found that the binding of the transcription factor, Yin Yang 1 (YY1), to hs3 and to the mu E1 site of the intronic enhancer, E mu, is induced in primary splenic B cells after approximately 48 h in response to LPS and other activators of class switch recombination. Transient transfection experiments in B cell lines indicate that YY1 is an activator of hs3. Interestingly, levels of YY1 expression are unchanged in resting and LPS-stimulated B cells. Mixing experiments followed by EMSA showed that a protein present in resting B cells prevented binding of YY1 to DNA. We found that recombinant retinoblastoma protein (Rb) inhibited binding of YY1 to hs3 in a dose-dependent manner, and we have identified complexes of endogenous YY1 with the Rb in resting B cells, but not in LPS-stimulated B cells. A difference in Rb phosphorylation state was also confirmed between resting (G(0)) B cells and LPS-stimulated B cells. These observations suggest that the interaction of YY1 with hypophosphorylated Rb in resting B cells prevents interaction of YY1 with DNA. After stimulation with class-switching activators, such as LPS, Rb becomes hyperphosphorylated and YY1 is released and can then bind to the hs3 enhancer and E mu."}

{"project":"2015-BEL-Sample-2","denotations":[{"id":"BEL:20000466","span":{"begin":1326,"end":1464},"obj":"complex(p(MGI:Yy1),p(MGI:Rb1)) decreases tscript(p(MGI:Yy1))"},{"id":"BEL:20000466","span":{"begin":1326,"end":1463},"obj":"complex(p(MGI:Yy1),p(MGI:Rb1)) decreases tscript(p(MGI:Yy1))"},{"id":"BEL:20035052","span":{"begin":1326,"end":1626},"obj":"complex(p(MGI:Yy1),p(MGI:Rb1)) decreases tscript(p(MGI:Yy1))"},{"id":"BEL:20060244","span":{"begin":1326,"end":1626},"obj":"p(MGI:Rb1) directlyDecreases tscript(p(MGI:Yy1))"}],"text":"Yin Yang 1 is a lipopolysaccharide-inducible activator of the murine 3' Igh enhancer, hs3.\nThe 3' Igh enhancers, DNase I hypersensitive site (hs) 3B and/or hs4, are required for germline transcription, and hence, class switch recombination for multiple isotypes. A number of hs3-binding transcription factors have been identified by EMSA, including octamer and NF-kappa B family members, and Pax5. We have found that the binding of the transcription factor, Yin Yang 1 (YY1), to hs3 and to the mu E1 site of the intronic enhancer, E mu, is induced in primary splenic B cells after approximately 48 h in response to LPS and other activators of class switch recombination. Transient transfection experiments in B cell lines indicate that YY1 is an activator of hs3. Interestingly, levels of YY1 expression are unchanged in resting and LPS-stimulated B cells. Mixing experiments followed by EMSA showed that a protein present in resting B cells prevented binding of YY1 to DNA. We found that recombinant retinoblastoma protein (Rb) inhibited binding of YY1 to hs3 in a dose-dependent manner, and we have identified complexes of endogenous YY1 with the Rb in resting B cells, but not in LPS-stimulated B cells. A difference in Rb phosphorylation state was also confirmed between resting (G(0)) B cells and LPS-stimulated B cells. These observations suggest that the interaction of YY1 with hypophosphorylated Rb in resting B cells prevents interaction of YY1 with DNA. After stimulation with class-switching activators, such as LPS, Rb becomes hyperphosphorylated and YY1 is released and can then bind to the hs3 enhancer and E mu."}