Computational Biology Center, IBM T.J. Watson Research Center, Yorktown Heights, NY 10598, USA. atsirigo@us.ibm.com|Computational Biology Center, IBM T.J. Watson Research Center, Yorktown Heights, NY 10598, USA. atsirigo@us.ibm.com|Computational Biology Center, IBM T.J. Watson Research Center, Yorktown Heights, NY 10598, USA. atsirigo@us.ibm.com|Computational Biology Center, IBM T.J. Watson Research Center, Yorktown Heights, NY 10598, USA. atsirigo@us.ibm.com