TY - JOUR
T1 - Multiple RNA-binding proteins function combinatorially to control the soma-restricted expression pattern of the E3 ligase subunit ZIF-1
AU - Oldenbroek, Marieke
AU - Robertson, Scott M.
AU - Guven-Ozkan, Tugba
AU - Gore, Steven
AU - Nishi, Yuichi
AU - Lin, Rueyling
N1 - Funding Information:
The authors would like to thank Lin lab members for discussions, Lesilee Rose for spn-2 cDNA, Kuppuswamy Subramaniam and Geraldine Seydoux for the germline expression vector, Geraldine Seydoux for JH1436, Yuji Kohara for the anti-SPN-4 antibody, Wormbase for valuable information, and C. elegans Genetics Center (CGC) for various strains. This work was supported by NIH grants ( HD37933 and GM84198 ) to R. L.
PY - 2012/3/15
Y1 - 2012/3/15
N2 - In C. elegans embryos, transcriptional repression in germline blastomeres requires PIE-1 protein. Germline blastomere-specific localization of PIE-1 depends, in part, upon regulated degradation of PIE-1 in somatic cells. We and others have shown that the temporal and spatial regulation of PIE-1 degradation is controlled by translation of the substrate-binding subunit, ZIF-1, of an E3 ligase. We now show that ZIF-1 expression in embryos is regulated by five maternally-supplied RNA-binding proteins. POS-1, MEX-3, and SPN-4 function as repressors of ZIF-1 expression, whereas MEX-5 and MEX-6 antagonize this repression. All five proteins bind directly to the zif-1 3' UTR in vitro. We show that, in vivo, POS-1 and MEX-5/6 have antagonistic roles in ZIF-1 expression. In vitro, they bind to a common region of the zif-1 3' UTR, with MEX-5 binding impeding that by POS-1. The region of the zif-1 3' UTR bound by MEX-5/6 also partially overlaps with that bound by MEX-3, consistent with their antagonistic functions on ZIF-1 expression in vivo. Whereas both MEX-3 and SPN-4 repress ZIF-1 expression, neither protein alone appears to be sufficient, suggesting that they function together in ZIF-1 repression. We propose that MEX-3 and SPN-4 repress ZIF-1 expression exclusively in 1- and 2-cell embryos, the only period during embryogenesis when these two proteins co-localize. As the embryo divides, ZIF-1 continues to be repressed in germline blastomeres by POS-1, a germline blastomere-specific protein. MEX-5/6 antagonize repression by POS-1 and MEX-3, enabling ZIF-1 expression in somatic blastomeres. We propose that ZIF-1 expression results from a net summation of complex positive and negative translational regulation by 3' UTR-binding proteins, with expression in a specific blastomere dependent upon the precise combination of these proteins in that cell.
AB - In C. elegans embryos, transcriptional repression in germline blastomeres requires PIE-1 protein. Germline blastomere-specific localization of PIE-1 depends, in part, upon regulated degradation of PIE-1 in somatic cells. We and others have shown that the temporal and spatial regulation of PIE-1 degradation is controlled by translation of the substrate-binding subunit, ZIF-1, of an E3 ligase. We now show that ZIF-1 expression in embryos is regulated by five maternally-supplied RNA-binding proteins. POS-1, MEX-3, and SPN-4 function as repressors of ZIF-1 expression, whereas MEX-5 and MEX-6 antagonize this repression. All five proteins bind directly to the zif-1 3' UTR in vitro. We show that, in vivo, POS-1 and MEX-5/6 have antagonistic roles in ZIF-1 expression. In vitro, they bind to a common region of the zif-1 3' UTR, with MEX-5 binding impeding that by POS-1. The region of the zif-1 3' UTR bound by MEX-5/6 also partially overlaps with that bound by MEX-3, consistent with their antagonistic functions on ZIF-1 expression in vivo. Whereas both MEX-3 and SPN-4 repress ZIF-1 expression, neither protein alone appears to be sufficient, suggesting that they function together in ZIF-1 repression. We propose that MEX-3 and SPN-4 repress ZIF-1 expression exclusively in 1- and 2-cell embryos, the only period during embryogenesis when these two proteins co-localize. As the embryo divides, ZIF-1 continues to be repressed in germline blastomeres by POS-1, a germline blastomere-specific protein. MEX-5/6 antagonize repression by POS-1 and MEX-3, enabling ZIF-1 expression in somatic blastomeres. We propose that ZIF-1 expression results from a net summation of complex positive and negative translational regulation by 3' UTR-binding proteins, with expression in a specific blastomere dependent upon the precise combination of these proteins in that cell.
KW - C. elegans
KW - Embryos
KW - Germline
KW - MEX-3
KW - MEX-5/6
KW - PIE-1
KW - POS-1
KW - SPN-4
KW - Translational repression
KW - Zif-1
UR - http://www.scopus.com/inward/record.url?scp=84857124037&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84857124037&partnerID=8YFLogxK
U2 - 10.1016/j.ydbio.2012.01.002
DO - 10.1016/j.ydbio.2012.01.002
M3 - Article
C2 - 22265679
AN - SCOPUS:84857124037
SN - 0012-1606
VL - 363
SP - 388
EP - 398
JO - Developmental Biology
JF - Developmental Biology
IS - 2
ER -