The mouse protein synthesis initiation factor 4A gene family includes two related functional genes which are differentially expressed.

Abstract

We have cloned and characterized a family of mouse genomic sequences hybridizing to mouse cDNA probes coding for eIF‐4A, one of the protein synthesis initiation factors involved in the binding of mRNA to the ribosome. We estimate that there is a total of approximately 9‐13 eIF‐4A pseudogenes. We also found an eIF‐4A intronless retroposon which, when compared to the cDNA, contains a single nucleotide difference. This possibly functional gene contains a mouse repetitive B1 element integrated in the promoter region. Furthermore, we have cloned two intron‐containing eIF‐4A genes (termed eIF‐4AI and eIF‐4AII). The eIF‐4AII gene codes for a previously unknown form of eIF‐4A. Northern blot hybridization with RNA from several mouse organs shows a variation in eIF‐4AI expression within a factor of 7. In contrast, relative to liver, eIF‐4AII expression is 20‐ to 30‐times higher in brain and kidney, 10‐ to 17‐fold higher in lung and heart, and is about equally abundant in liver, spleen and thymus. These data suggest that the relative efficiency of protein synthesis initiation for different mRNAs, as reflected by discrimination in messenger 5′‐terminal cap recognition and binding to ribosomes, varies in different tissues.

The Initiation Factor eIF4A Is Involved in the Response to Lithium Stress in Saccharomyces cerevisiae

“…In mouse two eIF4A proteins are expressed, eIF4AI and eIF4AII. The ratio of mRNA levels that encode for these two proteins varies among tissues, and it has been postulated that its concentration could influence the initiation process (33). RNA helicase activity is also induced by binding of eIF4A to eIF4F (14,34), eIF4B, and eIF4H (14).…”

Interactions between eIF4AI and its accessory factors eIF4B and eIF4H

“…4AI's proposed physiological role, and that of its highly homologous sibling eIF4AII (91% identical; Nielsen and Trachsel 1988), is to unwind RNA structures in the 59-UTR of mRNAs to facilitate 40S ribosomal subunit loading and subsequent AUG start codon identification. In vivo, 4AI constitutes one subunit of eIF4F, which also includes the 7-methyl-G cap binding protein eIF4E and the scaffolding protein eIF4G (4G) (Kapp and Lorsch 2004).…”

Translation and regulation of translation in the yeast Saccharomyces cerevisiae

“…Either one of the two genes is sufficient (and essential) for growth. S. cerevisiae eIF-4A is 65% identical with mouse eIF-4A [41]. It is involved, together with eIF-4B and eIF-4F, in mRNA binding to the 40s-Met-tRNAV complex ( Fig.…”