Takagaki Y, Seipelt R L, Peterson M L, Manley J L
Department of Biological Sciences, Columbia University, New York, New York 10027, USA.
Cell. 1996 Nov 29;87(5):941-52. doi: 10.1016/s0092-8674(00)82000-0.
The switch from membrane-bound to secreted-form IgM that occurs during differentiation of B lymphocytes has long been known to involve regulated processing of the heavy chain pre-mRNA. Here, we show that accumulation of one subunit of an essential polyadenylation factor (CstF-64) is specifically repressed in mouse primary B cells and that overexpression of CstF-64 is sufficient to switch heavy chain expression from membrane-bound (microm) to secreted form (micros). We further show that CstF-64 is limiting for formation of intact CstF, that CstF has a higher affinity for the microm poly(A) site than for the micros site, and that the microm site is stronger in a reconstituted in vitro processing reaction. Our results indicate that CstF-64 plays a key role in regulating IgM heavy chain expression during B cell differentiation.
长期以来，人们一直知道B淋巴细胞分化过程中发生的从膜结合型IgM到分泌型IgM的转变涉及重链前体mRNA的调控加工。在这里，我们表明，在小鼠原代B细胞中，一种必需的聚腺苷酸化因子（CstF-64）的一个亚基的积累受到特异性抑制，并且CstF-64的过表达足以将重链表达从膜结合型（microm）转换为分泌型（micros）。我们进一步表明，CstF-64对完整CstF的形成具有限制作用，CstF对microm聚腺苷酸化位点的亲和力高于对micros位点的亲和力，并且在体外重组加工反应中microm位点更强。我们的结果表明，CstF-64在B细胞分化过程中调节IgM重链表达方面发挥关键作用。
