The seven-transmembrane superfamily member 3 protein (TM7SF3) is a p53-regulated homeostatic factor that attenuates cellular stress and the unfolded protein response. Here we show that TM7SF3 localizes to nuclear speckles; eukaryotic nuclear bodies enriched in splicing factors. This unexpected location for a trans-membranal protein enables formation of stable complexes between TM7SF3 and pre-mRNA splicing factors including DHX15, LARP7, HNRNPU, RBM14, and HNRNPK. Indeed, TM7SF3 regulates alternative splicing of >330 genes, mainly at the 3′end of introns by directly modulating the activity of splicing factors such as HNRNPK. These effects are observed both in cell lines and primary human pancreatic islets. Accordingly, silencing of TM7SF3 results in differential expression of 1465 genes (about 7% of the human genome); with 844 and 621 genes being up- or down-regulated, respectively. Our findings implicate TM7SF3, as a resident protein of nuclear speckles and suggest a role for seven-transmembrane proteins as regulators of alternative splicing.
Bibliographical noteFunding Information:
Isolated human islets (∼90% purity) were provided by the European Consortium for Islets Transplantation (Islet for Basic Research program) through a Juvenile Diabetes Research Foundation Award 31-2008-413. Islets were cultured at 37°C in a 5% CO 2 humidified atmosphere in CMRL 1066 medium containing 10% (v/v) FBS, 2mM L-glutamine, 100 units/ml penicillin, 100 μg/mL streptomycin, 0.25 μg/mL amphotericin, and 40 μg/mL gentamycin. The medium was changed every other day. Human islets studies received the WIS Ethics Committee approval. Intact human islets were dispersed by a 4 min incubation at 37°C with 1 mg/ml Trypsin/EDTA and by passing the cells twice through a 21G needle. Trypsinized islets were washed with CMRL 1066 medium containing 10% FBS and were resuspended in CMRL 1066 containing 10% FBS.
Insightful discussions with Dr. Sanford Sampson (Bar Ilan University, Ramat Gan, Israel) are greatly acknowledged. YZ was supported by The Israel Science Foundation ( 776/13 ) and by the Samuil and Petr Polsky Prostate Cancer Research Fund ( 7218400101 ). ARM is supported by a UCSD /UCLA Diabetes Center Grant ( P30 DK063491 ) and by the NIH /NIDDK ( 1R01DK123422-01 ). N.D. was supported in part by a Ruth L. Kirschstein Institutional National Research Service Award T32 GM008666 from the National Institute of General Medical Sciences .
© 2022 The Authors
- Biological sciences
- Structural biology
ASJC Scopus subject areas