Structural homologies and functional similarities between mammalian origins of replication and amplification promoting sequences

Abstract

MuNTS2, a 423 bp sequence isolated from the non-transcribed spacer of murine rDNA stimulates the amplification of cis-linked plasmid DNA in mouse cells under selective conditions. Here we demonstrate that a 180 bp subdomain of muNTS2 is highly homologous (approximately 70%) to three domains of the first well-characterized origin of replication of mammalian chromosomes, i.e. the origin of bidirectional replication (OBR) of the dihydrofolate reductase (DHFR) locus in Chinese hamster ovary (CHO) cells. When subcloned, the 180 bp homology region of muNTS2 was revealed to be essential for the amplification promoting activity of muNTS2. Fragments of the initiation zone of DNA replication from the DHFR locus of hamster cells containing the domains of homology to the mouse muNTS2 element proved also to promote DNA amplification. Thus, the screening system for amplification promoting elements turned out to detect an origin of bidirectional replication.

Autonomous Plasmid Replication inAspergillus nidulans:AMA1 and MATE Elements

“…Amplification events are frequently associated with families of dispersed genomic repeats (the best known example is the human Alu repeat; Hyrien et al, 1987). Promoters of amplification are often able to initiate extrachromosomal replication (in the case of Alu repeats, see Johnson and Jelinek, 1986; also Stolzenburg et al, 1994). It is noteworthy that the best-studied origin of replication in mammalian cells is a part of the DHFR amplicon (Heintz et al, 1983).…”

Tobacco ribosomal DNA spacer element stimulates amplification and expression of heterologous genes

“…9), share common structural features. The A+T-rich tracks and repeated sequences homologous to yeast ARS (autonomously replicating sequence) consensus sequence, are among such structures 10,11 . When included into transfected vectors, these sequences have been shown to amplify adjacent genes up to 800 times and increase gene expression 9,12,13 .…”

Multiple Initiation Sites within the Human Ribosomal RNA Gene

“…This list includes origins associated with the genes encoding DHFR, [26][27][28][29][30] c-myc, 24,25,[31][32][33] β globin, [34][35][36][37][38] lamin B, 39,40 rhodopsin, 41 aldolase B, 42 Hsp70, 43 immunoglobulin heavy chain enhancer, 44 adenosine deaminase, 45 MCM4 and PRKDC 46 and the ribosomal RNA gene. Replication origins have been reported in the ribosomal RNA genes of a number of organisms, including human, [47][48][49][50] mouse, 51,52 rat, 49 schizosaccharomyces pombe, 53 saccharomyces cerevisiae, 54,55 tetrahymena thermophila, 56,57 pisum sativum 58 and tobacco chloroplast. 59 Within human ribosomal RNA genes, analyses of replication intermediate structures suggested a broad initiation zone covering the entire 30 kb non-transcribed spacer region (NTS), while other approaches suggest a highly preferred initiation region exists within a 5-10 kb NTS sequence upstream of the 18S transcribed sequence.…”