期刊
BIOCHEMICAL SOCIETY TRANSACTIONS
卷 32, 期 -, 页码 571-574出版社
PORTLAND PRESS LTD
DOI: 10.1042/BST0320571
关键词
chloroplast; helical repeat protein; pentatricopeptide repeat (PPR); plastid; RNA metabolism; RNA recognition motif
Chloroplast gene expression is mainly regulated at the post-transcriptional level by numerous nuclear-encoded RNA-binding protein factors. In the present study, we focus on two RNA-binding proteins: cpRNP (chloroplast ribonucleoprotein) and PPR (pentatricopeptide repeat) protein. These are suggested to be major contributors to chloroplast RNA metabolism. Tobacco cpRNPs are composed of five different proteins containing two RNA-recognition motifs and an acidic N-terminal domain. The cpRNPs are abundant proteins and form heterogeneous complexes with most ribosome-free mRNAs and the precursors of tRNAs in the stroma. The complexes could function as platforms for various RNA-processing events in chloroplasts. it has been demonstrated that cpRNPs contribute to RNA stabilization, 3'-end formation and editing. The l proteins occur as a superfamily only in the higher plant species. They are predicted to be involved in RNA/DNA metabolism in chloroplasts or mitochondria. Nuclear-encoded HCF152 is a chloroplast-localized protein that usually has 12 PPR motifs. The null mutant of Arabidopsis, hcflS2, is impaired in the 5'-end processing and splicing of petB transcripts. HCF152 binds the petB exon-intron junctions with high affinity. The number of PPR motifs controls its affinity and specificity for RNA. It has been suggested that each of the highly variable l proteins is a gene-specific regulator of plant organellar RNA metabolism.
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