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 (S ARs) and sequences able to replicate autonomously (ARSs) had been show n to comap on an 835-kb DNA fragment (Brun ct al. (1990) Mol. Cell. Bi ol. 10, 5455-5463), To investigate the question of whether this comapp ing results from the coincidental recruitment of SARs and ARSs in AT-r ich regions, A,T-rich regions of the 835-kb DNA fragment have been ide ntified by restriction analysis with enzymes recognizing motifs made e xclusively of A and T. Within the limits of sensitivity of this approa ch, 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 a ctivity, or an ARS activity, or both, nor are all SARs or ARSs localiz ed in the A,T-rich regions. In addition, the data support the idea tha t a statistical assessment of base composition using restriction analy sis might be developed into a general useful approach to genome organi zation. (C) 1995 Academic Press, Inc.