Evidence for conservation and selection of upstream open reading frames suggests probable encoding of bioactive peptides

Table 2 Frequency of downstream AUGs and ORFs.

	Human	Mouse
Number of mRNA sequences in initial dataset (1)	21597	14790
Number of mRNA sequences containing > 1 dAUG (2)	19853	14327
Total number of dAUGs (3)	352301	229945
Number of mRNA sequences containing > 1 dORF (4)	16965	11598
Total number of dORFs (5)	85876	55815
Number of mRNA sequences containing > 1 dORF after removal of duplicates (6)	14252	11377
Total number of dORFs after removal of duplicates (7)	69202	54403
Number of mRNA sequences containing > 1 dORF after removal of blast matches (8)	13899	11299
Total number of dORFs after removal of blast matches (9)	65258	52786

Frequency of downstream AUGs and ORFs (dAUGs and dORFs) in human and mouse RefSeq mRNA sequences. Initial dataset refers to all sequences of > 60 nucleotides annotated as 3' UTRs. Numbers in parentheses indicate the corresponding stage in the filtering flowchart (figure 1).

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