“…Additionally, we also incorporate the letter features to provide the same information as used in PWM-based approaches. As described in previous studies [14,28], letter features are generated by designating the four kinds of nucleotides -A, C, G, and T -as mutually orthogonal 4D vectors (1,0,0,0), (0,1,0,0), (0,0,1,0), and (0,0,0,1), respectively.…”