The fate of U1 snRNP during anti-Fas induced apoptosis: specific cleavage of the U1 snRNA molecule.
During apoptosis, the U1-70K protein, a component of the spliceosomal U1 snRNP complex, is specifically cleaved by the enzyme caspase-3, converting it into a C-terminally truncated 40-kDa fragment. In this study, we show that the 40-kDa U1-70K fragment is still associated with the complete U1 snRNP complex, and that no obvious modifications occur with the U1 snRNP associated proteins U1A, U1C and Sm-B/B'. Furthermore, it is described for the first time that the U1 snRNA molecule, which is the backbone of the U1 snRNP complex, is modified during apoptosis by the specific removal of the first 5 - 6 nucleotides including the 2,2, 7-trimethylguanosine (TMG) cap. The observations that U1 snRNA cleavage is very specific (no such modifications were detected for the other U snRNAs tested) and that U1 snRNA cleavage is markedly inhibited in the presence of caspase inhibitors, indicate that an apoptotically activated ribonuclease is responsible for the specific modification of U1 snRNA during apoptosis.
Degen
W G
WG
Department of Biochemistry, University of Nijmegen, NL-6500 HB Nijmegen, The Netherlands. w.degen@bioch.kun.nl
Aarssen
Y
Y
Pruijn
G J
GJ
Utz
P J
PJ
van Venrooij
W J
WJ
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001665:Binding Sites; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D006151:Guanosine / Q000031:analogs & derivatives / Q000378:metabolism; D018922:HL-60 Cells; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D051379:Mice; D009842:Oligopeptides / Q000494:pharmacology; D012314:RNA Cap Analogs / Q000378:metabolism; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000378:metabolism*; D019014:fas Receptor / Q000378:metabolism*
D000590:Amino Acid Chloromethyl Ketones; D000911:Antibodies, Monoclonal; D015853:Cysteine Proteinase Inhibitors; C098738:N-acetyl-tyrosyl-valyl-alanyl-aspartyl chloromethyl ketone; D009842:Oligopeptides; D012314:RNA Cap Analogs; D017412:Ribonucleoprotein, U1 Small Nuclear; C110772:benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone; C403753:benzyloxycarbonyl-isoleucyl-glutamyl-threonyl-aspartic acid fluoromethyl ketone; C403754:benzyloxycarbonyl-leucyl-glutamyl-histidyl-aspartic acid fluoromethyl ketone; D019014:fas Receptor; D006151:Guanosine; C017778:N(2),N(2),7-trimethylguanosine