A factor related to pseudouridine synthases is required for chloroplast group II intron trans-splicing in Chlamydomonas reinhardtii.
In Chlamydomonas reinhardtii, the psaA mRNA is assembled by a process involving two steps of trans-splicing that remove two group II introns and give rise to the mature mRNA. The products of at least 14 nuclear genes and one chloroplast gene (tscA) are necessary for this process. We have cloned Maa2, one of the nuclear genes involved in trans-splicing of the second intron. Maa2 encodes a protein with similarity to conserved domains of pseudouridine synthases, but mutagenesis of putative catalytic residues showed that this activity may not be required for trans-splicing of psaA RNA. Although it is not clear whether the pseudouridine synthase activity has been maintained in Maa2, it is possible that this enzyme was recruited during evolution as an RNA chaperone for folding or stabilizing the psaA intron. The Maa2 protein appears to be associated through ionic interactions with a low density membrane system in the chloroplast that also contains RNA-binding proteins involved in translation.
Perron
K
K
Departments of Molecular Biology and Plant Biology, University of Geneva, 30, Quai Ernest-Ansermet, 1211 Geneva, Switzerland.
Goldschmidt-Clermont
M
M
Rochaix
J D
JD
D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics*; D002467:Cell Nucleus / Q000235:genetics; D016825:Chlamydomonas reinhardtii / Q000235:genetics*; D002736:Chloroplasts / Q000235:genetics*; D003001:Cloning, Molecular; D005091:Exons; D006836:Hydro-Lyases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D007438:Introns; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D045331:Photosystem I Protein Complex; D015800:Protozoan Proteins; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D008565:Membrane Proteins; C073973:PSI-A protein, Synechococcus; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D015800:Protozoan Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D006836:Hydro-Lyases; C402788:Maa2 protein, Chlamydomonas; C022479:pseudouridylate synthetase