We constructed maps for eight chromosomes (1, 6, 9, 10, 13, 20, X and (previously) 22), representing one-third of the genome, by building landmark maps, isolating bacterial clones and assembling contigs. By this approach, we could establish the long-range organization of the maps early in the project, and all contig extension, gap closure and problem-solving was simplified by containment within local regions. The maps currently represent more than 94% of the euchromatic (gene-containing) regions of these chromosomes in 176 contigs, and contain 96% of the chromosome-specific markers in the human gene map. By measuring the remaining gaps, we can assess chromosome length and coverage in sequenced clones.

Knowledge of the complete genomic DNA sequence of an organism allows a systematic approach to defining its genetic components. The genomic sequence provides access to the complete structures of all genes, including those without known function, their control elements, and, by inference, the proteins they encode, as well as all other biologically important sequences. Furthermore, the sequence is a rich and permanent source of information for the design of further biological studies of the organism and for the study of evolution through cross-species sequence comparison. The power of this approach has been amply demonstrated by the determination of the sequences of a number of microbial and model organisms, The next step is to obtain the complete sequence of the entire human genome. Here we report the sequence of the euchromatic part of human chromosome 22. The sequence obtained consists of 12 contiguous segments spanning 33.4 megabases, contains at least 545 genes and 134 pseudogenes, and provides the first view of the complex chromosomal landscapes that will be found in the rest of the genome.

Earlier studies of psoriatic and normal primary keratinocytes treated with phorbol 12-myristate-1-acetate identified two low-molecular-weight proteins, termed phorbolin-1 (20 kDa; pI 6.6) and phorbolin-2 (17.6 kDa; pI 6.5). As a first step towards elucidating the role of these proteins in psoriasis, we report here the molecular cloning and chromosomal mapping of phorbolin-1 and a related cDNA that codes for a protein exhibiting a similar amino acid sequence. The phorbolins were mapped to position 22q13 immediately centromeric to the c-sis proto-oncogene. Transient expression of the phorbolin-1 cDNA in COS cells and by in vitro transcription/translation, yielded polypeptides that comigrated with phorbolins-1 and -2. Comparative sequence analysis revealed 22% overall identity and a similarity of 44% of the phorbolins to apobec-1, the catalytic subunit of the mammalian apolipoprotein B mRNA editing enzyme; however, recombinant-expressed phorbolin-1 exhibited no cytidine deaminase activity, using either a monomeric nucleoside or apolipoprotein B cRNA as substrate, and failed to bind an AU-rich RNA template. Whereas the precise function of the phorbolins remains to be elucidated, the current data suggest that it is unlikely to include a role in the post-transcriptional modification of RNA in a manner analogous to that described for apobec-1.