Abstract
In plasma cells, immunoglobulin heavy chain (IgH) secretory-specific mRNA is made in high abundance as a result of both increased promoter proximal poly(A) site choice and weak splice-site skipping. Ell2, the eleven-nineteen lysine rich leukemia gene, is a transcription elongation factor that is induced ∼6-fold in plasma cells and has been shown to drive secretory-specific mRNA production. Reducing ELL2 by siRNA, which reduced processing to the secretion-specific poly(A) site, also influenced the methylations of histone H3K4 and H3K79 on the IgH gene and impacted positive transcription factor b (pTEFb), Ser-2 carboxyl-terminal phosphorylation, and polyadenylation factor additions to RNA polymerase II. The multiple lineage leukemia gene (MLL) and Dot1L associations with the IgH gene were also impaired in the absence of ELL2. To investigate the link between histone modifications, transcription elongation, and alternative RNA processing in IgH mRNA production, we performed chromatin immunoprecipitation on cultured mouse B and plasma cells bearing the identical IgH γ2a gene. In the plasma cells, as compared with the B cells, the H3K4 and H3K79 methylations extended farther downstream, past the IgH enhancer to the end of the transcribed region. Thus the downstream H3K4 and H3K79 methylation of the IgH associated chromatin in plasma cells is associated with increased polyadenylation and exon skipping, resulting from the actions of ELL2 transcription elongation factor.
Highlights
RNA processing is altered when ELL2, a transcription elongation factor, is induced during differentiation to plasma cells
Plasma Cell Lines Express Higher Levels of Elongation Factors, Especially ELL2—Our rationale for these studies was that changes in mRNA processing to immunoglobulin heavy chain (IgH) secretion in plasma cells might be linked to changes in multiple elongation factors and subsequent histone modifications both in amount and distribution across the gene
We previously demonstrated that the addition of ELL2 can drive IgH secretory-specific mRNA production by facilitating exon skipping and proximal poly(A) site use [1]
Summary
RNA processing is altered when ELL2, a transcription elongation factor, is induced during differentiation to plasma cells. When B cells differentiate into plasma cells with their high levels of IRF-4, blimp-1, and ELL2 2 (eleven-nineteen lysine-rich leukemia gene 2), both the IgH mRNA is extensively polyadenylated at the secretory-specific site (sec-mRNA) and the splice between CH3 and M1 is skipped, precluding use of the downstream membrane exons [1]. The associations of ELL2, the SEC, Dot-com, and the polyadenylation factors that occur for these H3-lysine modifications are still unclear, but elucidating this sequence of events would aid in understanding the assembly of the transcription elongation complex in general and in elucidating IgH mRNA alternative processing in B cells versus plasma cells in particular. SiRNA inhibition of ELL2 significantly alters processing at the secretion-specific poly(A) site, it influences pTEFb and polyadenylation factor additions to the RNAP-II, MLL, and Dot1L associations with the gene. ELL2 is important for the histone modifications accompanying transition from membrane-specific to secretory IgH mRNA expression
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
