Multiple RNA surveillance mechanisms cooperate to reduce the amount of nonfunctional Ig kappa transcripts.
Random V(D)J junctions ensure that the diversity of the Ig primary repertoire is adapted to the vast heterogeneity of Ags. In two-thirds of cases, recombination between variable segments induces a frameshift in the open reading frame and generates a premature termination codon. In B cells harboring biallelic V(D)J rearrangement of Ig genes, transcription is known to occur on both the functional and nonfunctional alleles, generating considerable amounts of primary transcripts with out-of-frame V regions. In this study, we analyzed in cell lines and primary B cells the RNA surveillance of nonfunctional Igkappa transcripts arising from nonproductive rearrangement. We demonstrated that splicing inhibition, nonsense-mediated decay and nonsense-altered splicing each have an individual partial effect that together associate into an efficient surveillance machinery, downregulating nonfunctional Igkappa mRNA. Moreover, we provide evidence that the RNA surveillance efficiency increases throughout B cell development. Whereas splicing inhibition remains constant in most cell lines, differences in nonsense-mediated decay and nonsense-altered splicing are responsible for the higher RNA surveillance observed in plasma cells. Altogether, these data show that nonfunctionally rearranged alleles are subjected to active transcription but that multiple RNA surveillance mechanisms eradicate up to 90% of out-of-frame Igkappa mRNA.
Chemin
Guillaume
G
Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6101, Université de Limoges, Limoges, France.
Tinguely
Aurélien
A
Sirac
Christophe
C
Lechouane
Fabien
F
Duchez
Sophie
S
Cogné
Michel
M
Delpy
Laurent
L
D000483:Alleles; D000818:Animals; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D045744:Cell Line, Tumor; D018389:Codon, Nonsense / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D018388:Codon, Terminator / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D015536:Down-Regulation / Q000235:genetics* / Q000276:immunology*; D016368:Frameshift Mutation / Q000276:immunology; D015328:Gene Rearrangement, B-Lymphocyte, Light Chain / Q000276:immunology*; D007145:Immunoglobulin kappa-Chains / Q000235:genetics* / Q000502:physiology; D051379:Mice; D010950:Plasma Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D012326:RNA Splicing / Q000276:immunology*; D012333:RNA, Messenger / Q000037:antagonists & inhibitors* / Q000502:physiology; D011995:Recombination, Genetic / Q000276:immunology*; D013234:Stem Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D014158:Transcription, Genetic / Q000276:immunology*
D018389:Codon, Nonsense; D018388:Codon, Terminator; D007145:Immunoglobulin kappa-Chains; D012333:RNA, Messenger