Duplication of ATR inhibits MyoD, induces aneuploidy and eliminates radiation-induced G1 arrest

Abstract

Chromosome 3q alterations occur frequently in many types of tumours. In a genetic screen for loci present in rhabdomyosarcomas, we identified an isochromosome 3q [i(3q)], which inhibits muscle differentiation when transferred into myoblasts. The i(3q) inhibits MyoD function, resulting in a non-differentiating phenotype. Furthermore, the i(3q) induces a 'cut' phenotype, abnormal centrosome amplification, aneuploidy and loss of G1 arrest following gamma-irradiation. Testing candidate genes within this region reveals that forced expression of ataxia-telangiectasia and rad3-related (ATR) results in a phenocopy of the i(3q). Thus, genetic alteration of ATR leads to loss of differentiation as well as cell-cycle abnormalities.

Chromosomes with delayed replication timing lead to checkpoint activation, delayed recruitment of Aurora B and chromosome instability

“…All were grown in Dulbecco's modified Eagle's medium with 10% fetal bovine serum (Hyclone Laboratories, Logan, UT, USA). The microcell hybrid C2i(3q)-1 was derived from RH30 cells (from Dr P Houghton) (Smith et al, 1998) and the C2(3n)-1 are C2C12 microcell hybrids containing an intact chromosome 3, derived from GM11713 (ATCC). R268 cells, derived from HTD114 fibrosarcoma cell line contain a t(15;16)(q24;q12.1) generated using Cre/lox (Breger et al, 2005).…”

“…Individual cells can contain multiple chromosomes with the DMC phenotype, and the DMC chromosomes within a given cell can display a wide range in the extent of mitotic chromosome condensation (Figure 1c-f) (Smith et al, 1998). Furthermore, chromosomes with the more extreme undercondensed appearance lack the Figure 1 Variability of condensation on chromosomes with DRT/DMC from C2C12 microcell hybrids containing i(3q) (Smith et al, 2001).…”

An ATM- and ATR-dependent checkpoint inactivates spindle assembly by targeting CEP63

“…It is thought that ATR-ATRIP, as part of the DNA replication machinery, associated with RPA, monitors single stranded DNA damage during the progression of DNA replication fork elongation (Niida and Nakanishi, 2006;Shechter et al, 2004b). In addition, ATR functions in both S and M phases include regulating late DNA replication origin firing, replication fork elongation, restarting stalled replication forks and involvement in centrosome stability (Shechter et al, 2004a;Cha and Kleckner, 2002;Sorensen et al, 2004;Friedel et al, 2009;Alderton et al, 2004;Smith et al, 1998).…”

Rhabdomyosarcoma – working out the pathways

“…This LOI can lead to a twofold gene dosage e ect, and may contribute to the characteristic overexpression of IGF2 observed in these tumors (Zhan et al, 1994). LOH studies have Barr et al, 1993;Galili et al, 1993Davis et al, 1994Besnard-Gue rin et al, 1996Visser et al, 1997Stratton et al, 1990Mulligan et al, 1990;Felix et al, 1992El-Badry et al, 1990Zhan et al, 1994Meddeb et al, 1996Keleti et al, 1996;Fiddler et al, 1996Khatib et al, 1993Knudsen et al, 1998Ferracini et al, 1996Garson et al, 1986Mitani et al, 1986;Bayani et al, 1995Weber-Hall et al, 1996Smith et al, 1998Iolascon et al, 1996Schweigerer et al, 1987De Giovanni et al, 1995Chardin et al, 1985Stratton et al, 1989 *Denotes alterations seen commonly in both RMS cell lines and tumor tissue; other lesions occur occasionally, and/or have been infrequently reported. LOH, loss of heterozygosity; LOI, loss of imprinting also suggested the existence of putative RMSassociated tumor suppressor genes residing at 11q and 16q (Loh et al, 1992;Visser et al, 1997).…”