Another transcript containing different exons 1a and 1b instead of the original exon 1 identified by 5 RACE has also been reported7
Another transcript containing different exons 1a and 1b instead of the original exon 1 identified by 5 RACE has also been reported7. Open in a separate window Figure 1 Human gene structure and isoformsAlternative splicing generates 3 forms of mRNA. fates at a molecular level. Understanding SALL4s molecular functions will allow development of specific targeted approaches in the future. (SALL) gene family (to (Gene and Protein Structure In humans, is located in 20q13.2, consisting of four coding exons and 3,162 bp of coding sequence (mRNA, 1851bp) and “type”:”entrez-nucleotide”,”attrs”:”text”:”AY170622″,”term_id”:”37727662″,”term_text”:”AY170622″AY170622 (mRNA, 831bp) suggest that two alternative splicing products exist in addition to the full length mRNA. The B mRNA consists of exon 1, 1,020 bp of 5 end of exon 2, exons 3 and 4, whereas in the C mRNA, exon 2 is spliced out 6 (Figure 1). Another transcript containing different exons 1a and 1b instead of the original exon 1 identified by 5 RACE has also been reported7. Open in a separate window Figure 1 Human gene structure and isoformsAlternative splicing generates 3 forms of mRNA. (encoding 1053 amino acids) has all 4 exons and contains 4 zinc finger domains (ZF1C4, indicated by blue bars). (encoding 617 a.a.) is generated via an alternative splice donor site that results in the deletion of large portion of exon 2 and a protein that contains only ZF1 and ZF4. (encoding 277 a.a.) does not have exon 2 and encodes a version that only has ZF1. A conserved N-terminal 12 amino acid (N-12aa) domain of SALL4 (indicated by red bars) is sufficient for recruiting the nucleosome remodeling and histone deacetylase (NuRD) complex and mediating transcriptional repression. A glutamine (Q)-rich region (indicated by yellow bars) that is highly conserved in all invertebrate and vertebrate family members, was shown to be necessary in protein interactions between Spalt family proteins. A conserved nuclear localization signal (NLS) has been reported and is indicated by green bars. Like the protein encoded by RNA and Sall4 protein become enriched in the inner cell mass (ICM) and the trophectoderm. Finally, by E11.5, Sall4 expression is observed in the midbrain, the rostral edge of the forebrain, maxillary arch, genital tubercle, limb buds, tail, and left ventricular myocardium17,18. In adult mice, Sall4 expression is mostly restricted to germ cells, wherein it is highly expressed in undifferentiated spermatogonia and oocytes in primordial, primary, and secondary follicles19,20,21. Similarly, expression of SALL4 in adult human tissue is restricted to the testis and ovary4 (Figure 2). One exception to this expression pattern is human CD34+ hematopoietic stem/progenitor cells (HSPCs)22. Open in a separate window Figure 2 SALL4 expression during developmentSall4 protein expression is first observed at the two-cell stage, and later in some cells of EC-PTP the 8- to 16-cell-stages of the mouse embryo. In late blastocysts, Sall4 protein becomes enriched in the inner cell mass (ICM) and the trophectoderm. By E11.5, Sall4 expression is observed in the midbrain, genital tubercle, limb and tail buds17,18. In adult mice, Sall4 expression is mostly restricted to the germ cells, wherein it is highly expressed in undifferentiated spermatogonia and oocytes in primordial, primary, and Batimastat (BB-94) secondary follicles19,20,21. The red circles represent SALL4 expression. has isoform-specific gene expression pattern in the testis, ESCs, and fetal liver cells. is expressed in postnatal day 7 (PND7) testis, while is expressed from PND0 onward 23. is more abundant than in undifferentiated mouse ESCs, and neither isoform is found upon induction of ESC differentiation11. Furthermore, the A isoform, and not B, is detected in fetal livers, while several human hepatocellular carcinoma (HCC) cell lines express both and Gene Regulation Very little is known about the expression regulation of and its isoforms. Several studies have focused on the promoter region of this gene7,25,26. While one study reported on was proposed to be a downstream target gene of STAT325. During intestinal metaplasia of the gastric epithelial cells, was identified as a direct target of Caudal-related homeobox 1 (CDX1) protein28. In murine ESC, several reports have demonstrated that Sall4 protein participates in an interconnected autoregulatory circuit with Oct4, Sox2, and Nanog, wherein each of the four factors can regulate its own expression as well as that of others29,30,31. Within this circuit, one study reported that Sall4 can negatively self-regulate and antagonize Oct4s activation function to balance its own Batimastat (BB-94) expression level26. Batimastat (BB-94) Further, a TCF/LEF consensus sequence was reported in the.