Increased phosphorylation of the carboxyl-terminal domain of RNA polymerase II and loading of polyadenylation and cotranscriptional factors contribute to regulation of the ig heavy chain mRNA in plasma cells.
B cells produce Ig H chain (IgH) mRNA and protein, primarily of the membrane-bound specific form. Plasma cells produce 20- to 50-fold higher amounts of IgH mRNA, most processed to the secretory specific form; this shift is mediated by substantial changes in RNA processing but only a small increase in IgH transcription rate. We investigated RNA polymerase II (RNAP-II) loading and phosphorylation of its C-terminal domain (CTD) on the IgG2a H chain gene, comparing two mouse cell lines representing B (A20) and plasma cells (AxJ) that express the identical H chain gene whose RNA is processed in different ways. Using chromatin immunoprecipitation and real-time PCR, we detected increased RNAP-II and Ser-2 and Ser-5 phosphorylation of RNAP-II CTD close to the IgH promoter in plasma cells. We detected increased association of several 3' end-processing factors, ELL2 and PC4, at the 5' end of the IgH gene in AxJ as compared with A20 cells. Polymerase progress and factor associations were inhibited by 5,6-dichlorobenzimidazole riboside, a drug that interferes with the addition of the Ser-2 to the CTD of RNAP-II. Taken together, these data indicate a role for CTD phosphorylation and polyadenylation/ELL2/PC4 factor loading on the polymerase in the choice of the secretory poly(A) site for the IgH gene.
Shell
Scott A
SA
Department of Immunology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Martincic
Kathleen
K
Tran
Joseph
J
Milcarek
Christine
C
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D001483:Base Sequence; D002460:Cell Line; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation / Q000379:methods; D007143:Immunoglobulin Heavy Chains / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010950:Plasma Cells / Q000276:immunology*; D026723:Polyadenylation / Q000276:immunology; D017434:Protein Structure, Tertiary; D012319:RNA Polymerase II / Q000276:immunology* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000276:immunology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012694:Serine / Q000276:immunology / Q000378:metabolism*; D014158:Transcription, Genetic / Q000235:genetics* / Q000276:immunology
D007143:Immunoglobulin Heavy Chains; D012333:RNA, Messenger; D012694:Serine; D012319:RNA Polymerase II