The third human homolog of a murine gene encoding an inhibitor of stem cell proliferation is truncated and linked to a CpG island-containing upstream sequence

The normal copy of the G0S19-3-associated, CpG island-containing, upstream sequence is downstream of G0S19-2/MIP1alpha in association with a TRE17 oncogene

The G0S19-1/MIP1alpha and G0S19-2/MIP1alpha genes locate to human chromosomes 17q and encode similar copies of the beta-chemokine G0S19/MIP1alpha. The G0S19-3 gene, present in 1 in 4 humans, is a 5' truncated version of G0S19-2; a CpG island-containing upstream sequence (CpG-US), rich in potential transcriptional activation motifs, replaces much of the first intron and the first exon. Sequences hybridizing with the CpG-US sequence, normally exist in all human genomes. Thus, it appears that there has been recombination between a duplicated G0S19 gene and a duplicated CpG-US-like sequence. We have isolated sequences hybridizing with the CpG-US sequence from a human genomic library in bacteriophage lambda. Restriction mapping and sequencing shows a CpG-US-like sequence approximately 8 kb downstream of G0S19-2 (hence, named CpG-DS sequence). The sequence is contiguous with a TRE17 oncogene-associated sequence (GenBank locus HSTRE175). Members of the TRE17 family are known to locate to chromosome 17q (Onno et al., 1993b), and have sequence characteristics suggestive of positive Darwinian selection. Linkage with a TRE17 oncogene may have arisen by recombination and imply no functional relationship. However, it is possible that the CpG-DS may normally regulate TRE17 expression. PCR and sequencing studies indicate the close proximity of other chemokine-related sequences in the 17q11.2 region.

A human gene encoding a putative basic helix-loop-helix phosphoprotein whose mRNA increases rapidly in cycloheximide-treated blood mononuclear cells

G0S8 is a member of a set of putative G0/G1 switch regulatory genes (G0S genes) selected by screening cDNA libraries prepared from blood mononuclear cells cultured for 2 hr with lectin and cycloheximide. Comparison of a full-length cDNA sequence with the corresponding genomic sequence reveals an open reading frame of 211 amino acids, distributed across 5 exons. The 24-kD protein has a basic domain preceding a potential helix-loop-helix domain which contains a QTK motif found about 60 amino acids from the carboxyl terminus in the loop region of several helix-loop-helix proteins. There are potential phosphorylation sites for protein kinase C, creatine kinase II, and protein tyrosine kinases and regions of sequence similarity to helix-loop-helix proteins, tyrosine phosphatases, and RNA and DNA polymerases. The genomic sequence contains a CpG island, suggesting expression in the germ line. Potential binding sites for transcription factors are present in the 5' flank and introns; these include Zif268/NGFI-A/EGR1/G0S30, NGFI-B, Ap1, and factors that react with retroviral long terminal repeats (LTRs). There are several potential interferon response elements and a serum response element in the 3' flank overlapping a region of similarity to a cytomegalovirus immediate-early gene enhancer. Many of these motifs are found in immediate-early G0/G1 switch genes; however, we were unable to demonstrate an increase in G0S8 mRNA in response to lectin alone. Sequence similarities are noted between G0S8 and a variety of genes involved in the immune system, in the regulation of retroviruses, and in the cell cycle.