Characterization of a promoter and a transcription terminator of Spiroplasma melliferum virus SpV4.

摘要: Spiroplasma virus 4 (SpV4) is an isometric with single-stranded, circular DNA infecting the helical mollicute melliferum, a honeybee pathogen. Previous studies in our laboratory led to determination of base sequence SpV4 DNA. Nine open reading frames and three promoterlike sequences (P1, P2, P3) were identified. An inverted repeat leading formation hairpin structure on transcription product was also found predicted be terminator (T). We have now studied vivo genome by Northern (RNA) blot analysis total RNAs extracted from SpV4-infected spiroplasma cells. Transcripts 7.8, 4.4, 3.4, 2.7 kilobases (kb) detected. The 3.4-kb RNA major transcript. 5' 3' ends this transcript determined S1 mapping primer extension. Characterization end showed that terminates within stretch uridine residues following T. indicated proceeds newly recognized promoter, P0, located 36 nucleotides upstream P1. Primer extension resulted two cDNA signals. short probably artifact due presence When reverse transcriptase stopped at or read through, long cDNA, respectively, obtained. size identified P0 as promoter. Promoter shown functional Escherichia coli. Indeed, when inserted chloramphenicol acetyltransferase gene promoter selection vector, it promoted gene. As case S. cDNAs obtained extension, longer identifying