Features of the Influenceof a DNA Sequence on ItsAdjacent Sequence

To explore the features of the influence of a DNA sequence (here called sequence A) on its adjacent sequence (here called sequence B), we linked some DNA repeated sequences to the 5′-end of the T7 promoter in the plasmid pET-42a (+) or the 5′- and/or 3′-end(s) of the EcoRI site in some DNA fragments using PCR and other molecular cloning methods. As a result, we found that the efficiency of the T7 promoter and EcoRI could be impacted by some flanking sequences, indicating that sequence B could be impacted by sequence A. The features of such influence include the following: (i) sequence A can directly impact sequence B without changing/modifying the base composition of sequence B or destroying the inherent connection between sequence B and its function-related sequences; (ii) such influence does not need the participation of trans-acting factors or products of sequence A (if any); (iii) such an influence might be undetectable when the activities of trans-acting factors of sequence B are normal but might become detectable when those are lower than the normal one; (iv) such an influence might be enhancive, inhibitory, or unobvious; (v) the influence of sequence A linked to the 5′-end of sequence B might be the same as or opposite to that of sequence A linked to the 3′-end; and (vi) the influences of sequence A linked to different ends of sequence B could enhance or partially offset each other when sequence A is linked to both 5′- and 3′-ends of sequence B. These findings might give us a further understanding of the interaction of two adjacent DNA sequences.