SARS, ARSS, AND A,T-RICH REGIONS EVIDENCED BY RESTRICTION MAPPING ON AN 835-KB DNA FRAGMENT FROM DROSOPHILA

In Drosophila, sequences anchoring the DNA molecule to the scaffold (SARs) and sequences able to replicate autonomously (ARSs) had been shown to comap on an 835-kb DNA fragment (Brun ct al. (1990) Mol. Cell. Biol. 10, 5455-5463), To investigate the question of whether this comapping results from the coincidental recruitment of SARs and ARSs in AT-rich regions, A,T-rich regions of the 835-kb DNA fragment have been identified by restriction analysis with enzymes recognizing motifs made exclusively of A and T. Within the limits of sensitivity of this approach, the obtained data favor the idea of a noncoincidental recruitment: obviously a SAR and an ARS subpopulation are preferentially localized in the AT-rich regions, but not every AT-rich region displays a SAR activity, or an ARS activity, or both, nor are all SARs or ARSs localized in the A,T-rich regions. In addition, the data support the idea that a statistical assessment of base composition using restriction analysis might be developed into a general useful approach to genome organization. (C) 1995 Academic Press, Inc.