Figure 1

Coding potential statistics for mamastrovirus (human-porcine-feline astrovirus clade) ORF2 and the overlapping ORFX. (1) Map of the ORF2 region of human astrovirus [GenBank: Z25771], showing the proposed new coding sequence, ORFX, overlapping ORF2 in the +1 reading frame. (2-6) Coding potential statistics based on an alignment of 88 mamastrovirus sequences with complete coverage ORF2 (see Methods for accession numbers). For clarity, regions with alignment gaps in the arbitrary reference sequence (viz. Z25771) have been removed (e.g. regions where a single sequence in the alignment has an insertion, resulting in alignment gaps in all the other sequences). (2-4) Positions of stop codons in each of the three forward reading frames. The +0 frame corresponds to ORF2 and is therefore devoid of stop codons. Note the conserved absence of stop codons in the +1 frame within the ORFX region. (5-6) Conservation at synonymous sites within ORF2 (see [5] for details). (5) depicts the probability that the degree of conservation within a given window could be obtained under a null model of neutral evolution at synonymous sites, while (6) depicts the absolute amount of conservation as represented by the ratio of the observed number of substitutions within a given window to the number expected under the null model. Note the unusually high conservation within the ORFX region.