Functional redundancy of worm spliceosomal proteins U1A and U2B″

doi:10.1073/pnas.0701720104

Functional redundancy of worm spliceosomal proteins U1A and U2B″

*Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, Aurora, CO 80045; and
^†Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309

Edited by Barbara J. Meyer, University of California, Berkeley, CA, and approved April 25, 2007 (received for review February 23, 2007)

Abstract

In Caenorhabditis elegans, the small nuclear ribonucleoprotein (snRNP)-associated proteins U1A and U2B″ are ≈50% identical to each other, and neither bears signature characteristics of mammalian U1A or U2B″ or the single Drosophila homolog, SNF. We show here that the genes that encode these proteins (rnp-2 and rnp-3) are cotranscribed in an operon, and that ribonucleoprotein RNP-2 is U1 snRNP-associated (U1A) whereas RNP-3 is U2 snRNP-associated (U2B″). U2B″ interacts with U2 even in the absence of another U2 snRNP protein, U2A′. Like U1A and U2B″ from yeast, plants, and vertebrates, worm U1A and U2B″ are more similar to each other than they are to other U1A or U2B″ proteins, respectively. Even though U1A and U2B″ interact with different snRNPs, they are functionally redundant; knockout of both is required for a lethal phenotype. Interestingly, U1A associates with U2 RNA when U2B″ is deleted. Thus, the two members of this gene family normally function as components of different snRNPs but apparently remain capable of performing the function of the other. Redundancy results from the fact that one protein can substitute for the other, even though it normally does not.

Footnotes

^§To whom correspondence should be addressed. E-mail: tom.blumenthal{at}colorado.edu
Author contributions: T.S., C.W., M.M., and T.B. designed research; T.S. and C.W. performed research; T.S., M.M., and T.B. analyzed data; and T.S., M.M., and T.B. wrote the paper.
↵ ^‡Present address: Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
Abbreviations:

RRM,

RNA recognition motif;

snRNP,

small nuclear ribonucleoprotein.