B. Yan et Dr. Pring, TRANSCRIPTIONAL INITIATION SITES IN SORGHUM MITOCHONDRIAL-DNA INDICATE CONSERVED AND VARIABLE FEATURES, Current genetics, 32(4), 1997, pp. 287-295
Transcriptional initiation and processing was examined for three sorgh
um mitochondrial DNA genes (atp6-1, atp6-2, urf209) and two open readi
ng frames (orf265/130, orf107) to characterize sequences associated wi
th initiation and other transcriptional strategies for this species. T
he 5' termini of ten transcripts were determined by primer extension,
and mtRNA was capped with guanylyl transferase and annealed to anti-se
nse riboprobes to identify transcriptional initiation regions. Eight t
ranscript termini were suitable substrates for guanylyl transferase, i
ndicating the presence of one (atp6-1, atp6-2, urf209), two (orf265/13
0), or three (orf107) promoters for the five examples. The majority of
the putative promoters were associated with single primer-extension t
ermini, while two examples exhibited two transcript-initiation sites w
ithin the promoter. Four examples were characterized by initiated tran
scripts without subsequent processing, indicating that processing is n
ot obligatory. Each of the putative promoter regions included signific
ant A/T-rich 5' regions, consistent with previous examples, but four e
xceptions to a consensus core YRTA sequence were identified. The anoma
lies (AATA, CTTA) suggest plasticity in the primary structure of the c
ore region of higher-plant mitochondrial DNA promoters.