TY - JOUR
T1 - Yin Yang 1 is a lipopolysaccharide-inducible activator of the murine 3′ Igh enhancer, hs3
AU - Gordon, Steven J.
AU - Saleque, Shireen
AU - Birshtein, Barbara K.
PY - 2003/6/1
Y1 - 2003/6/1
N2 - The 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-κB family members, and Pax5. We have found that the binding of the transcription factor, Yin Yang 1 (YY1), to hs3 and to the μE1 site of the intronic enhancer, Eμ, is induced in primary splenic B cells after ∼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 (Go) 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 Eμ.
AB - The 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-κB family members, and Pax5. We have found that the binding of the transcription factor, Yin Yang 1 (YY1), to hs3 and to the μE1 site of the intronic enhancer, Eμ, is induced in primary splenic B cells after ∼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 (Go) 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 Eμ.
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U2 - 10.4049/jimmunol.170.11.5549
DO - 10.4049/jimmunol.170.11.5549
M3 - Article
C2 - 12759432
AN - SCOPUS:0037514314
SN - 0022-1767
VL - 170
SP - 5549
EP - 5557
JO - Journal of Immunology
JF - Journal of Immunology
IS - 11
ER -