Journal: Nucleic Acids Research
Article Title: RNA self-cleavage activated by ultraviolet light-induced oxidation
Figure Lengend Snippet: Characterization of UV-C cleavage of viral RNAs by fingerprinting and electrophoretic methods. ( a ) The RNA fingerprints of internally [α- 32 P] HCV (panels 1–3) and CSFV RNA (panels 4–6). Labeled SM, band B1 and band B2 were exhaustively digested with RNase T1 and the products subjected to 2D separation. ( 1 ) RNA fingerprint of HCV 1–249. A total of 500 000 dpm of HCV SM was fingerprinted. Spot 1: the HCV oligonucleotide 5′ 78 UCUAG 82 3′ within which cleavage takes place; Spot 2: this has the characteristic mobility of the 5′-terminal nucleotide 5′pppGp3′. ( 2 ) RNA fingerprint of HCV B1. A total of 300 000 dpm of RNA was fingerprinted as above. Spot 1 has disappeared, while the absence of the 5′-end (spot 2) shows that HCV B1 contains the 3′-portion of SM. ( 3 ) Fingerprint of HCV B2 (100 000 dpm). ‘1’ indicates the loss of spot 1, while the presence of the HCV 5′-end (‘2’) shows that HCV B2 contains the 5′-portion of SM. ( 4–6 ): RNA fingerprints of CSFV 1-218. SM (500 000 dpm), B1 (300 000 dpm) and B2 (100 000 dpm, transcribed with all four [α- 32 P]-labeled rNTPs. ‘1’: the CSFV oligonucleotide 5′ 38 AUACACUAAAUUUCG 52 3′, which is present in SM but absent from B1 and B2; ‘X’ (a new CSFV B1 oligonucleotide) and ‘Y’ (the other new CSFV oligonucleotide) arise from cleavage within spot 1 (see text) . ‘2’: the 5′-end of CSFV, present in SM and B2, but not B1. Numbering according to Wang et al. ( 62 ) for HCV genotype 1b and Gene Bank J04358 for CSFV Alfort Isolate. The sequence of the spot numbered as 1 was identified by secondary RNase analysis and high voltage electrophoresis on DEAE and Whatmann paper by Hugh D. Robertson (data not available), as well as by superposition with previously resolved HCV fingerprints using secondary analysis and on the basis of the rules for RNA oligonucleotide mobility during 2D TLC. Briefly, these rules are: the larger the oligonucleotide, the slower the migration of the corresponding spot to the bottom. As far as composition is concerned, Us displace the spot to the left, Cs to the right, and As cause a slight delay, thus meaning that several As in the same oligo may cause it to behave as an oligo containing one or even two additional bases ( 37 ). As far as sequence is concerned, as HCV RNA was transcribed in the presence of [α- 32 P]GTP here, those T1 oligonucleotides in the original sequence that are followed by a (pG) carry a double label. In the case of HCV RNA several RNase T1 oligonucelotides are indicated as mobility reference: a: UCCUUUCUUGp(G); b: UCUUCAGp(C) 61:68; c: CUCAAUGp(G) 211–217; d: AUUUGp(G) 225–229. Spot 1 locates in the border of the triangle that can be formed by spots i, f and g. In CSFV, spot 1 is the slow migrating spot, and thus corresponded to the largest RNase T1 oligonucleotide. In both HCV and CSFV, band B2 contains the original 5′-terminal nucleotide, pppGp, of the substrate RNA transcript (indicated by ‘2’). The disappearance of spot 1 from both product band fingerprints (see Figure 1 a, images 2, 3 and images 5, 6) suggests that self-cleavage occurs within this oligonucleotide and that this event is specific. Moreover, in the case of CSFV RNA two smaller oligomers (X and Y) that represent the fragment products of spot 1 are observed within the fingerprints of both product bands (B1 and B2) for CSFV. Indicated at the bottom is the sequence surrounding RNase T1 cleavage sites. ( b ) Electrophoresis analysis: Autoradiogram showing a parallel run of HCV RNA 1–130 and CSFV RNA 1–218 UV-cleavage reaction, with RNase T1 treated samples and control reactions for transcripts labeled at either the 5′-extreme with [γ- 32 P]GTP during transcription or the 3′-extreme with [5′- 32 P]pCp and T4 RNA ligase. HCV (lanes 1–6) and CSFV (lanes 1–9). HCV: Lanes 1 and 1′: RNAs incubated in standard buffer; lanes 2 and 2′: RNAs treated with RNase T1 under denaturing conditions; lanes 3 and 3′: RNA irradiated with UV-C light for 180 s. CSFV: Lanes 1 and 1′: RNAs incubated under standard conditions; lanes 2, 3 and 4′: RNA treated with RNase T1; lanes 4 and 3′: RNA irradiated with UV-C light: Lanes 5 and 2′ RNAs partially degraded with alkali. ‘G’ positions of a relevant size are indicated on either side of the gels. Lines indicate SM, and products B1 and B2.
Article Snippet: RNA ligase was used to treat cleavage product bands, either previously phosphatase treated or not, as follows: RNAs were incubated at 4°C for 4 days in a buffer containing 10 mM MgCl2 , 50 mM HEPES, pH 8.3, 5 mM DTT, 0.12 mM ATP, 4 U of T4 RNA ligase (Promega) and [5′-32 P]pCp (Perkin-Elmer) ( , ).
Techniques: Labeling, Sequencing, Electrophoresis, Thin Layer Chromatography, Migration, Incubation, Irradiation