Tristetraprolin, a negative regulator of mRNA stability, is increased in old B cells and is involved in the degradation of E47 mRNA.
We have previously shown that the E2A-encoded transcription factor E47, which regulates class switch in splenic B cells, is down-regulated in old B cells, due to increased E47 mRNA decay. At least part of the decreased stability of E47 mRNA seen in aged B cells is mediated by proteins. We have herein looked at the specific proteins responsible for the degradation of the E47 mRNA and found that tristetraprolin (TTP), a physiological regulator of mRNA expression and stability, is involved in the degradation of the E47 mRNA. Although many studies have characterized TTP expression and function in macrophages, monocytes, mast cells, and T cells, little is known about the expression and function of TTP in primary B cells. We show herein that TTP mRNA and protein expression are induced by LPS in B cells from young and old mice, the levels of TTP in old B cells always being higher than those in young B cells. Although TTP mRNA is degraded at a significantly higher rate in old B cells, TTP mRNA expression is higher in old than in young, likely due to its increased transcription. Like in macrophages, TTP protein expression and function in B cells are dependent upon p38 MAPK. We found that there is less phospho-TTP (inactive form), as well as phospho-p38, in old than in young splenic-activated B cells. This is the first report showing that TTP is involved in the degradation of the E47 mRNA and is up-regulated in old B cells.
Frasca
Daniela
D
Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL 33101, USA.
Landin
Ana Marie
AM
Alvarez
Juan P
JP
Blackshear
Perry J
PJ
Riley
Richard L
RL
Blomberg
Bonnie B
BB
D000375:Aging / Q000276:immunology*; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D015153:Blotting, Western; D024202:Electrophoretic Mobility Shift Assay; D005260:Female; D047468:Immunoprecipitation; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051820:TCF Transcription Factors / Q000235:genetics / Q000378:metabolism*; D058125:Transcription Factor 7-Like 1 Protein; D014162:Transfection; D051816:Tristetraprolin / Q000276:immunology* / Q000378:metabolism; D015854:Up-Regulation
D012333:RNA, Messenger; D051820:TCF Transcription Factors; C544913:Tcf7l1 protein, mouse; D058125:Transcription Factor 7-Like 1 Protein; D051816:Tristetraprolin