The stability of the Chlorella nitrate reductase mRNA is determined by the secondary structure of the 5'-UTR: implications for posttranscriptional regulation of nitrate reductase.
Nitrate reductase (NR; EC 1.6.1.1-3) can be controlled at both transcriptional and posttranscriptional levels. Here we describe stability of NR mRNA as a mechanism of control. The NR gene in Chlorella vulgaris (Warburg strain) transcribes a stable mRNA and an unstable mRNA. In-vitro-synthesized transcripts representing these mRNAs show the same stability characteristics. The unstable mRNA is 30 nucleotides longer at the 5'-UTR compared to the stable mRNA. Using an RNA-folding program the 5'-UTR of the longer unstable RNA showed a more extensive stem-loop structure compared to the more linear form of the shorter stable mRNA. Transcripts representing RNAs with intermediate 5'-UTRs folded similarly to the long form and were unstable, or similarly to the short form and were more stable. Thus the secondary structure of the 5'-UTR of NR mRNA is important in the stability of NR transcripts in Chlorella and allows the cell to respond to changes in nitrogen source in an energy-efficient manner.
Cannons
Andrew C
AC
Department of Biology, University of South Florida, Tampa 33620, USA. acannons@chuma.cas.usf.edu
Cannon
Jennifer
J
D020121:5' Untranslated Regions / Q000737:chemistry / Q000235:genetics; D002708:Chlorella / Q000201:enzymology* / Q000235:genetics; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000235:genetics*; D009690:Nucleic Acid Conformation; D012323:RNA Processing, Post-Transcriptional; D020871:RNA Stability; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D020121:5' Untranslated Regions; D012333:RNA, Messenger; D009565:Nitrate Reductases; D050901:Nitrate Reductase