Zinc finger-like structure in U1-specific protein C is essential for specific binding to U1 snRNP.
The U1 small nuclear ribonucleoprotein (snRNP) contains three specific proteins denoted 70K, A and C, in addition to the common proteins. Specific functions of these proteins are not known although recently protein C was shown to be involved in the binding of U1 snRNP to the 5' splice site of a pre-mRNA. Unlike proteins A and 70K, U1-C lacks an RNA binding domain (RNP-80 motif) and does not appear to bind directly to U1 snRNA. However, at the amino terminal end protein C contains a zinc finger-like structure of the CC-HH type found in transcription factor TF IIIA. Several lines of evidence indicate that the zinc finger-like structure is essential for the binding of protein C to U1 snRNP particles: i) deletion analysis of protein C showed that the N-terminal 45 amino acids are sufficient for binding to U1 snRNPs, ii) modification of the cysteine residues in the N-terminal domain with N-ethylmaleimide and iii) single point mutations of the cysteines and histidines contributing to the putative zinc finger abolished binding of protein C to U1 snRNPs. Interestingly, unlike the proteins U1-A and U1-70K the U1-C protein is unable to bind to naked U1 snRNA. On the other hand it is shown that protein C does not bind to the known protein constituents of the U1 particle without the U1 snRNA being present. These data indicate that the binding of protein C to U1 snRNP is dependent on the presence of both the U1 snRNA and one or more of the U1 snRNP proteins.
Nelissen
R L
RL
Department of Biochemistry, University of Nijmegen, The Netherlands.
Heinrichs
V
V
Habets
W J
WJ
Simons
F
F
Lührmann
R
R
van Venrooij
W J
WJ
D000595:Amino Acid Sequence; D004252:DNA Mutational Analysis; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D011485:Protein Binding; D012342:RNA, Small Nuclear / Q000378:metabolism*; D011994:Recombinant Proteins; D012261:Ribonucleoproteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D017411:Ribonucleoproteins, Small Nuclear; D013329:Structure-Activity Relationship; D016335:Zinc Fingers
D012342:RNA, Small Nuclear; D011994:Recombinant Proteins; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear