J Biol Chem, Vol. 274, Issue 50, 35955-35962, December 10, 1999
Target and Specificity of a Nuclear Gene Product That
Participates in mRNA 3'-End Formation in Chlamydomonas
Chloroplasts*
Haim
Levy
§,
Karen L.
Kindle¶
, and
David B.
Stern
**
From the
Boyce Thompson Institute for Plant Research
and the ¶ Plant Science Center, Cornell University,
Ithaca, New York 14853-1801
Chloroplast mRNA maturation is catalyzed by
nucleus-encoded processing enzymes. We previously described a recessive
nuclear mutation (crp3) that affects 3'-end formation of
several chloroplast mRNAs in Chlamydomonas reinhardtii
(Levy, H., Kindle, K. L., and Stern, D. B. (1997) Plant
Cell 9, 825-836). In the crp3 background, atpB mRNA lacking a 3'-inverted repeat normally
required for stability accumulates as a discrete transcript. The
mutation also affects the atpA gene cluster; polycistronic
mRNAs with psbI or cemA 3'-ends accumulate
to a lower level in the crp3 background. Here, we
demonstrate that the crp3 mutation also alters 3'-end
formation of psbI mRNA and cemA-containing
mRNAs. A novel 3'-end is formed in monocistronic psbI
transcripts, and this is the only terminus observed when the
psbI 3'-untranslated region is fused to an aadA
reporter gene. Accumulation of mRNAs with 3'-ends between
cemA and atpH, which is immediately downstream,
was reduced. However, this sequence was not recognized as a 3'-end
formation element in chimeric genes. The crp3 mutation was
able to confer stability to three different atpB
3'-stem-loop-disrupting mutations that lack sequence similarity, but
are located at a similar distance from the translation termination codon. We propose that the wild-type CRP3 gene product is
part of the general 3'
5' processing machinery.
*
This work was supported by National Science Foundation Award
MCB-9723274.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.