Alternative titles; symbols
HGNC Approved Gene Symbol: GIMAP4
Cytogenetic location: 7q36.1 Genomic coordinates (GRCh38): 7:150,567,390-150,573,953 (from NCBI)
By searching a sequence database using IMAP1 (608084) as probe, Stamm et al. (2002) identified IMAP4. The deduced 329-amino acid protein contains 5 motifs conserved in GTP-binding proteins and a putative C-terminal coiled-coil region. IMAP4 shares 44% amino acid identity with IMAP1. Phylogenetic analysis indicated that IMAP4 is homologous to mouse Ian1.
By representational difference analysis of transcripts regulated by TAL1 (187040), Cambot et al. (2002) cloned IMAP4, which they called IAN1, from a Jurkat T-cell line cDNA library. Cambot et al. (2002) noted that the GTPase-like motifs of IAN1 have substitutions in residues considered key in other GTPases. Northern blot analysis detected high expression of IAN1 in spleen and peripheral blood leukocytes, with lower expression in thymus, small intestine, colon, and ovary. No expression was detected in prostate or testis. Among mature hematopoietic cells, RT-PCR detected IAN1 only in B and T cells.
Cambot et al. (2002) found that recombinant IAN1 expressed in E. coli showed efficient and saturable GDP binding in a filter binding assay. Binding was highly dependent on Mg(2+) concentration. IAN1 did not bind GMP, and it had higher affinity for GDP than for a nonhydrolyzable analog of GTP. Recombinant IAN1 also showed intrinsic GTPase activity. During T- and B-lymphocyte activation, IAN1 expression was regulated at the posttranscriptional level. Cambot et al. (2002) transfected IAN1 into a murine pre-B hematopoietic cell line that was completely dependent on IL3 (147740) for cell proliferation and survival. Following IL3 withdrawal, IAN1 expression led to a G2/M cell cycle arrest.
Stamm et al. (2002) determined that the IMAP4 gene contains 3 exons. Exon 1 is untranslated, and exon 3 contains more than 94% of the coding sequence. The homologous mouse gene, Ian1, contains 4 exons. Exons 1 and 4 are untranslated, and exon 2 encodes the first 19 amino acids.
By genomic sequence analysis, Stamm et al. (2002) mapped the IMAP4 gene to a 100-kb IMAP gene cluster on chromosome 7q32-q36. Within this cluster, IMAP1 is located on the negative strand, while IMAP2 (GIMAP2; 608085), IMAP3 (GIMAP5; 608086), and IMAP4 are on the opposite positive strand.
Cambot, M., Aresta, S., Kahn-Perles, B., de Gunzburg, J., Romeo, P.-H. Human immune associated nucleotide 1: a member of a new guanosine triphosphatase family expressed in resting T and B cells. Blood 99: 3293-3301, 2002. [PubMed: 11964296] [Full Text: https://doi.org/10.1182/blood.v99.9.3293]
Stamm, O., Krucken, J., Schmitt-Wrede, H.-P., Benten, W. P. M., Wunderlich, F. Human ortholog to mouse imap38 encoding an ER-localizable G-protein belongs to a gene family clustered on chromosome 7q32-q36. Gene 282: 159-167, 2002. [PubMed: 11814688] [Full Text: https://doi.org/10.1016/s0378-1119(01)00837-x]