CD19 function in early and late B cell development. II. CD19 facilitates the pro-B/pre-B transition.

Proliferative expansion of pro-B cells is an IL-7-dependent process that allows for the rearrangement of H chain genes and the expression of the pre-B cell receptor (pre-BCR). Further B cell differentiation is dependent upon signals elicited through the pre-BCR, which are thought to be responsible for allelic exclusion, induced L chain gene rearrangement, and continued proliferation. CD19 promotes the proliferation and survival of mature B cells, but its role in early B cell development is less well understood.

Arginine methylation of STAT1 regulates its dephosphorylation by T cell protein tyrosine phosphatase.

Transcriptional induction by interferons requires the tyrosine and serine phosphorylation of the STAT1 transcription factor as well as its amino-terminal arginine methylation. Here we show that arginine methylation of STAT1 controls the rate of STAT1 dephosphorylation by modulating its interaction with PIAS1 and the nuclear tyrosine phosphatase TcPTP. Inhibition of STAT1 arginine methylation, or mutation of STAT1 Arg-31, results in a prolonged half-life of STAT1 tyrosine phosphorylation.