We have searched the human genome for genes encoding new proteins that may be involved in three nuclear gene expression processes: transcription, pre-messenger RNA splicing and polyadenylation. A plethora of potential new factors are implicated by sequence in nuclear gene expression, revealing a substantial but selective increase in complexity compared with Drosophila melanogaster and Caenorhabditis elegans. Although the raw genomic information has limitations, its availability offers new experimental approaches for studying gene expression.