[Cloning, structure and features of a Saccharomyces cerevisiae DNA fragment causing the expression of reporter genes]. / Klonirovanie, struktura i osobennosti uchastka DNK Saccharomyces cerevisiae, vyzyvaiushchego ékspressiiu reporternykh genov.

A DNA fragment "PX" of 240 b.p. was isolated at random from the genomic sequences of S. cerevisiae by using a plasmid that contained a promoterless reporter gene lacZ of E. coli. "PX" was capable of activating synthesis of three reporter genes (pho5 from yeast and bacterial lacZ and neo) in yeast cells bidirectionally. Results of Southern-blot hybridization with yeast genomic DNA suggest that the cloned sequence is represented in at least ten copies per cell. Nucleotide sequence of "PX" shows that DNA contains putative TATA elements and four tandems of inverted repeats: [sequence: see text].

[Structure of nuclear pre-mRNA. XI. Triphosphorylated and blocked 5'-ends in the pre-mRNA]. / Struktura iadernoi pro-mRNK. XI. Trifosforilirovannye i blokirovannye 5'-kontsy v pro-mRNK.

The nature of the 5'-termini in pre-mRNA isolated from Ehrlich carcinoma cells has been investigated. To discriminate between triphosphorylated 5'-ends and capped structures different methods were used including treatment by alkaline phosphatase and several chromatographic methods. It was shown that heavey pre-mRNA contains a significant number of non-blocked triphosphorylated nucleotides at the 5'-end termini. However, phosphatase resistent, blocked 5'-termini were also found. 5'-terminal nucleotides in triphosphorylated pre-mRNA are G in a 3 : 2 ratio. In contrast to nuclear pre-mRNA cytoplasmic poly(A)+mRNA does not contain triphosphorylated 5'-ends but does contain the "cap" structure only. To elucidate the pre-mRNA topography the localization of homopolymeric regions of pre-mRNA, poly(A) and oligo(U), in relation to 5'terminal structures has been investigated. The experiments showed that the distance between 3'-terminal poly(A) sequences and 5'-end triphosphates is longer than 1500--2000 nucleotides. At the same time the distance between the latter and oligo(U) in pre-mRNA is much shorter.