Fig. 4

Structure and gene control function of the SDC motif. a Consensus model depicting the conserved sequences and predicted secondary structure of SDC motif RNAs. Annotations are as described in Fig. 1. b Sequence and secondary structure model for the SDC motif representative from N. crassa. Nucleotides depicted in red correspond to the most highly conserved nucleotides present in the consensus sequence in a. M1 through M5 identify nucleotide differences at the positions indicated in mutant constructs used to assess the importance of the P1 stem to gene expression. c Schematic representation of the genetic elements present near the SDC motif, including the location of the luciferase reporter gene used for RT-PCR and reporter-fusion gene expression assays. Arrows identify primer binding sites used for RT-PCR. Dashed lines identify splicing variations using one of the two 5ˊ splice sites (GU) and the 3ˊ splice site (AG) that can convert the precursor mRNA (Pre) into the alternative splicing products Sp-I and Sp-II. The graphic is not drawn to scale. d Agarose gel separation of RT-PCR products generated from SDC reporter fusion transcript in N. crassa. The absence (–) or presence (+) of reverse transcriptase (RT) in the assay is indicated. The asterisk denotes an RT-PCR product whose identity was not confirmed by DNA sequencing. M indicates double-stranded DNA markers. The two images depict neighboring parts of the same gel. e Gene expression of wild-type (WT) and mutant SDC reporter-fusion constructs. Relative light units were normalized to WT (value of 1). The values are an average of three independent replicates, and error bars represent standard deviation