College of Computer and Information Science, Northeastern University, Boston, MA 02115, USA.|Department of Computer Science and Engineering, University of Washington, Seattle, WA 98195, USA.|Department of Biochemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.|Department of Biochemistry.|Genome Center.|Department of Computer and Information Science, University of Massachusetts Dartmouth, Dartmouth, MA 02747, USA.|College of Computer and Information Science, Northeastern University, Boston, MA 02115, USA.