TY - JOUR
T1 - Processing of the psbA 5' untranslated region in Chlamydomonas reinhardtii depends upon factors mediating ribosome association
AU - Bruick, Richard K.
AU - Mayfield, Stephen P.
PY - 1998/11/30
Y1 - 1998/11/30
N2 - The 5' untranslated region of the chloroplast psbA mRNA, encoding the D1 protein, is processed in Chlamydomonas reinhardtii. Processing occurs just upstream of a consensus Shine-Dalgarno sequence and results in the removal of 54 nucleotides from the 5' terminus, including a stem-loop element identified previously as an important structure for D1 expression. Examination of this processing event in C. reinhardtii strains containing mutations within the chloroplast or nuclear genomes that block psbA translation reveals a correlation between processing and ribosome association. Mutations within the 5' untranslated region of the psbA mRNA that disrupt the Shine-Dalgarno sequence, acting as a ribosome binding site, preclude translation and prevent mRNA processing. Similarly, nuclear mutations that specifically affect synthesis of the D1 protein specifically affect processing of the psbA mRNA. In vitro, loss of the stem-loop element does not prohibit the binding of a message-specific protein complex required for translational activation of psbA upon illumination. These results are consistent with a hierarchical maturation pathway for chloroplast messages, mediated by nuclear-encoded factors, that integrates mRNA processing, message stability, ribosome association, and translation.
AB - The 5' untranslated region of the chloroplast psbA mRNA, encoding the D1 protein, is processed in Chlamydomonas reinhardtii. Processing occurs just upstream of a consensus Shine-Dalgarno sequence and results in the removal of 54 nucleotides from the 5' terminus, including a stem-loop element identified previously as an important structure for D1 expression. Examination of this processing event in C. reinhardtii strains containing mutations within the chloroplast or nuclear genomes that block psbA translation reveals a correlation between processing and ribosome association. Mutations within the 5' untranslated region of the psbA mRNA that disrupt the Shine-Dalgarno sequence, acting as a ribosome binding site, preclude translation and prevent mRNA processing. Similarly, nuclear mutations that specifically affect synthesis of the D1 protein specifically affect processing of the psbA mRNA. In vitro, loss of the stem-loop element does not prohibit the binding of a message-specific protein complex required for translational activation of psbA upon illumination. These results are consistent with a hierarchical maturation pathway for chloroplast messages, mediated by nuclear-encoded factors, that integrates mRNA processing, message stability, ribosome association, and translation.
KW - Chloroplast
KW - Ribosome binding sequence
KW - Translation
KW - mRNA processing
KW - psbA
UR - http://www.scopus.com/inward/record.url?scp=0032583118&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0032583118&partnerID=8YFLogxK
U2 - 10.1083/jcb.143.5.1145
DO - 10.1083/jcb.143.5.1145
M3 - Article
C2 - 9832545
AN - SCOPUS:0032583118
SN - 0021-9525
VL - 143
SP - 1145
EP - 1153
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 5
ER -