Molecular cloning and expression of the mouse translation initiation factor eIF-1A

Prior to determining the molecular basis for the transient increase in expression of eIF-1A during the 2-cell stage of the pre-implantation mouse embryo, we determined the sequence of full-length cDNA and defined properties of the genomic organization of the mouse eIF-1A gene. Northern blot analysis distinguishes three transcripts in mouse liver of 2.8, 2.2 and 1.9 kb in size. The three transcripts arise from initiation at two putative promoters separated by 627 bp. Initiation from the putative distal promoter yields both the 2.8 and 1.9 kb transcripts, in which the 1.9 kb transcript is generated by alternative splicing of 840 bp of intervening RNA. The putative distal promoter, which lacks both a TATA box and CCAAT box control elements but contains several GC-rich clusters, initiates transcription at two start sites that are separated by 30 bp. Thus, four transcripts are generated from the distal promoter. The putative proximal promoter that directs transcription of a single 2.2 kb mRNA is preceded by a TATA box element that binds TBP. Each of the promoters is used by the pre-implantation mouse embryo, since we have been able to amplify selectively each of the five individual eIF-1A transcripts initiated from each promoter and start site in the 2-cell mouse embryo.