An initiation site of DNA replication with transcriptional enhancer activity present upstream of the c-myc gene.

Abstract

We have previously reported that c‐myc protein may promote cellular DNA replication by binding to initiation sites of replication. Here we report that a putative origin of human cellular DNA replication (ori) is present at approximately 2 kb upstream of the coding region of the c‐myc gene itself. The c‐myc protein, or protein(s) complexed with c‐myc protein, bind to the upstream region (approximately 200 bp in length) which has transcriptional enhancer activity as well as autonomously replicating activity in human cells, suggesting that the c‐myc protein may be an enhancer binding protein as well as a DNA replication protein. Results with deletion mutants suggest that the sequence essential to the origin of DNA replication may be adjacent to, but cannot be clearly separated from, the sequence responsible for enhancer activity. Furthermore, when cloned DNA containing putative c‐myc protein binding sequences was transfected as competitor into HL‐60 cells, expression of c‐myc was inhibited, suggesting that c‐myc protein itself may be necessary for c‐myc expression.

Autonomous replication of human chromosomal DNA fragments in human cells.

“…Using the density labeling procedure employed here, we have tested the replication activity of several ARS plasmids isolated in other laboratories, including Vol. 4, November 1993 pORS9 and pORS12 (Frappier and Zannis-Hadjopoulos, 1987), pmyc-HP (Iguchi- Ariga et al, 1988), and pHgrl6 (Krysan et al, 1989). pHgrl6, which carries an -15-kb-long human chromosomal segment, replicated in 293S cells at an efficiency similar to that of plWl, whereas pORS9, pORS12, or pmyc-HP did not replicate significantly (Masukata, unpublished data).…”

“…Several chromosomal fragments have been reported to replicate autonomously in human or monkey cells (Frappier and Zannis-Hadjopoulos, 1987;Iguchi-Ariga et al, 1988;Krysan et al, 1989;McWhinney and Leffak, 1990). Using the density labeling procedure employed here, we have tested the replication activity of several ARS plasmids isolated in other laboratories, including Vol.…”

MSSP promotes ras/myc cooperative cell transforming activity by binding to c‐Myc

“…In addition to various regulatory elements for transcription and replication in the human c-myc gene, we have identi®ed a putative replication origin and transcriptional enhancer about 2 kb upstream from the ®rst exon (Iguchi- Ariga et al 1988). The 21 base pairs therein were required for both transcription and replication activities and bound by a c-Myc complex (Ariga et al 1989;Negishi et al 1992).…”

The Origin Recognition Complex Marks a Replication Origin in the Human TOP1 Gene Promoter

“…One major conclusion of these experiments is that, whereas the replication of genomes in differentiated mammalian and other metazoan cells begins at specific genomic loci that are quite stably inherited from one cell division cycle to the next, individual origins of a given organism differ greatly in size and sequence and are clearly less uniform and more complex in structure than budding yeast origins (3-5, 9, 10, 24). Many known mammalian origins are found to be located between transcribed regions and frequently in the vicinity of active transcriptional start sites (25)(26)(27)(28). One reason for a preferred location of origins at transcriptional start sites might be the more loosely organized chromatin structure, allowing initiator replication proteins better access to their target DNA binding sites (for a recent review, see Ref.…”