Answer:
Through a specific base sequence.
Step-by-step explanation:
OCT1 is a protein that acts as a gene transcription factor.
For RNA polymerase to be able to find the starting point of transcription it needs proteins known as Transcription Factors. These proteins are responsible for binding to specific DNA sequences (promoters) that characterize the transcription start site and recruiting RNA polymerase to these sites.
Thus, we can say that for OCT1 to be able to bind to DNA it must recognize a sequence of specific nitrogenous bases in DNA that fits its binding motif.