Abstract
The multifunctional eukaryotic protein YB-1 (Y-box binding protein 1) plays a role in DNA reparation, transcription regulation, splicing, and mRNA translation, thereby participating in many crucial events in cells. Its effect is dependent mostly on its amount, and hence, on regulation of its synthesis. Published data on regulation of synthesis of YB-1 mediated by its mRNA 5′ UTR, and specifically on the 5′ UTR length and the presence of TOP-like motifs in this region, are contradictory. Here we report that 5′ UTRs of major forms of human, rabbit, and mouse YB-1 mRNAs are about 140 nucleotides long and contain no TOP-like motifs mentioned in the literature. Also, we have found that YB-1 specifically interacts with the 5′ UTR of its own mRNA within a region of about 100 nucleotides upstream from the start codon. Apart from YB-1, translation of YB-1 mRNA in a cell free system gives an additional product with an extended N-terminus and lower electrophoretic mobility. The start codon for synthesis of the additional product is AUC at position –(60–58) of the same open reading frame as that for the major product. Also, in the cell there is an alternative YB-1 mRNA with exon 1 replaced by a part of intron 1; YB-1 synthesized in vitro from this mRNA contains, instead of its N-terminal A/P domain, 10–11 amino acids encoded by intron 1.
Highlights
The multifunctional nucleocytoplasmic protein YB-1 (Y-box binding protein 1, YB-1, YBX1) is a member of the large family of cold shock domain containing proteins [1]
In one case only (YB-1 mRNA from HEK293 cells) this value was 118, which could be the result of a reverse transcription interruption at the first stage of RACE, probably caused by CG-rich regions within the YB-1 mRNA 59 UTR
To measure the length of 59 UTRs by an independent technique, samples of total RNA from human (HeLa and HEK293) and mouse (NIH3T3) cells and from rabbit reticulocytes were treated with RNase H in the presence of a 21 nt DNA oligonucleotide that was complimentary to the YB-1 mRNA sequence 150–170 nt downstream from the translation start codon (Fig. 1A)
Summary
The multifunctional nucleocytoplasmic protein YB-1 (Y-box binding protein 1, YB-1, YBX1) is a member of the large family of cold shock domain containing proteins [1] It is a protein with intrinsically disordered spatial structure that allows its interactions with DNA, RNA, and a large number of proteins. The wide variety of YB-1 functions dictates the necessity of strict control over its amount in the cell, which depends on the rates of its synthesis and decay The former is determined by both efficiency of YB-1 transcription and efficiency of YB-1 mRNA translation; in turn, the latter depends on both the 39 UTR [3,4,5,6] and the 59 UTR of YB-1 mRNA [7,8]
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