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Group II intron splicing factors derived by diversification of an ancient RNA‐binding domain
Author(s) -
Ostheimer Gerard J.,
WilliamsCarrier Rosalind,
Belcher Susan,
Osborne Erin,
Gierke Jennifer,
Barkan Alice
Publication year - 2003
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/cdg372
Subject(s) - biology , intron , rna splicing , group ii intron , genetics , rna binding protein , rna , splicing factor , group i catalytic intron , diversification (marketing strategy) , evolutionary biology , computational biology , gene , marketing , business
Group II introns are ribozymes whose catalytic mechanism closely resembles that of the spliceosome. Many group II introns have lost the ability to splice autonomously as the result of an evolutionary process in which the loss of self‐splicing activity was compensated by the recruitment of host‐encoded protein cofactors. Genetic screens previously identified CRS1 and CRS2 as host‐encoded proteins required for the splicing of group II introns in maize chloroplasts. Here, we describe two additional host‐encoded group II intron splicing factors, CRS2‐associated factors 1 and 2 (CAF1 and CAF2). We show that CRS2 functions in the context of intron ribonucleoprotein particles that include either CAF1 or CAF2, and that CRS2–CAF1 and CRS2–CAF2 complexes have distinct intron specificities. CAF1, CAF2 and the previously described group II intron splicing factor CRS1 are characterized by similar repeated domains, which we name here the CRM ( c hloroplast R NA splicing and ribosome m aturation) domains. We propose that the CRM domain is an ancient RNA‐binding module that has diversified to mediate specific interactions with various highly structured RNAs.