B-cell and plasma-cell splicing differences: A potential role in regulated immunoglobulin RNA processing

Abstract

The immunoglobulin µ pre-mRNA is alternatively processed at its 3 end by competing splice and cleavage-polyadenylation reactions to generate mRNAs encoding the membrane-associated or secreted forms of the IgM protein, respectively. The relative use of the competing processing pathways varies during B-lymphocyte development, and it has been established previously that cleavage-polyadenylation activity is higher in plasma cells, which secrete IgM, than in B cells, which produce membraneassociated IgM. To determine whether RNA-splicing activity varies during B-lymphocyte development to contribute to µ RNA-processing regulation, we first demonstrate that µ pre-mRNA processing is sensitive to artificial changes in the splice environment by coexpressing SR proteins with the µ gene. To explore differences between the splice environments of B cells and plasma cells, we analyzed the splicing patterns from two different chimeric non-Ig genes that can be alternatively spliced but have no competing cleavage-polyadenylation reaction. The ratio of intact exon splicing to cryptic splice site use from one chimeric gene differs between several B-cell and several plasma-cell lines. Also, the amount of spliced RNA is higher in B-cell than plasma-cell lines from a set of genes whose splicing is dependent on a functional exonic splice enhancer. Thus, there is clear difference between the B-cell and plasma-cell splicing environments. We propose that both general cleavage-polyadenylation and general splice activities are modulated during B-lymphocyte development to ensure proper regulation of the alternative µ RNA processing pathways.

Expression of a Dromedary Heavy Chain-Only Antibody and B Cell Development in the Mouse

“…2C) and surface expression (Fig. 2E, top bands) were found, both in bone marrow and spleen cells, as has been described for mRNA products in mouse B cells (37). Figure 2, D and F, illustrate the exon usage of the PCR products, which have been confirmed by cloning and sequencing (supplemental Table I).…”

Gene regulation by sense–antisense overlap of polyadenylation signals

“…In polyomavirus, read-through of the late poly(A) site leads to up-regulation of late mRNA levels because the read-through transcripts allow new and productive splicing events to occur. This is reminiscent of the regulation of the production of mRNAs encoding the membrane-associated or secreted forms of the IgM protein, where alternative splicing is masked by efficient polyadenylation or transcription termination (Bruce et al 2003). The difference in the polyoma system is that regulation is achieved by the RNA structure or editing of signals rather than by modulation of polyadenylation or splicing factors.…”

Hide and Go Seek: Activation of the Secretory-Specific Poly (A) Site of Igh by Transcription Elongation Factors

“…LPS induction of splenic B-cells increases CstF-64 and introduction of CstF-64 into chicken DT40 B-cells results in Ig secretion (Takagaki, Seipelt et al 1996), see Table 1. Both the Igh 5' splice site in the last sec exon and the sec poly(A) sites are weak and in competition (Peterson and Perry 1989); overall splicing is decreased in plasma cells (Bruce, Dingle et al 2003). A shift in the SR-proteins is seen from the activating type (ASF/SF2) in B-cells to the repression type (SRp20) in plasma cells.…”

“…The balance between these has been shown to control many genes, reviewed in (House and Lynch 2008). Changes in the levels of the splicing factors in various B cell types (Bruce, Dingle et al 2003) and during development have been shown to alter splicing patterns (Expert-Bezancon, Sureau et al 2004). For, example, SRp20 plays an important role in alternative splicing of the ED1 exon (de la Mata and Kornblihtt 2006).…”

“…In B-cells, U1A (Milcarek, Martincic et al 2003), hnRNP F (Veraldi, Arhin et al 2001), and Serine-Arginine-rich (SR) proteins like ASF/SF2 (Bruce, Dingle et al 2003) are expressed in relatively higher concentrations than in plasma cells. The CTD of RNAP-II on the Igh gene is relatively under-phosphorylated; the polyadenylation factors CPSF and CstF and ELL2 are not strongly associated (Shell, Martincic et al 2007) with the polymerase.…”