Evolutional insights on uncharacterized SARS coronavirus genes

The complete genome of the severe acute respiratory syndrome coronavirus (SARS-CoV) and many of its variants has been determined by several laboratories. The genome contains fourteen predicted open reading frames (ORFs). However, a function had been clearly assigned for only six of these ORFs, in the viral replication, transcription and structural constituents. The others are herein referred to as uncharacterized ORFs (UC-ORFs). Here, we try to provide a relational insight on those UC-ORFs, suggesting that a number of them are remotely related to structural proteins of coronaviruses and other viruses infecting mammalian hosts. Surprisingly, several of the UC-ORFs exhibit considerable similarity with other SARS-CoV ORFs. These observations may provide clues on the evolution and genome dynamics of the SARS-CoV.