Molecular advances in the cell biology of SARS-CoV and current disease prevention strategies

Stark, Caren J; Atreya, CD

To date, approximately 61 SARS-CoV genomic sequences have been analyzed representing different phases of the epidemic (early, middle, and late) and two isolates obtained from palm civets [18] . The SARS-CoV genomic RNA is approximately 30 kb and is organized into 13 to 15 open reading frames (ORFs) [25] [26] [27] . The SARS CoV structural gene arrangement follows the same pattern as most coronavirus genomes: [27] . However, in contrast to other coronaviruses, two ORFs of unknown function are located between the S and E ORFs and 3-5 ORFs are located between M and N. In addition, despite the evolutionary overlap between SARS-CoV and Group II coronavirus genome sequences, the SARS genome lacks a gene for hemagglutinin-esterase (HE) protein, which is common to a majority of Group II coronaviruses [25] . For an excellent pictorial representation of SARS-CoV genome with functions (or lack of) assigned to each ORF, please refer to the recent review by Tan et al [21] . A significant milestone in SARS-CoV molecular biology was the construction of a SARS-CoV full-length cDNA-containing plasmid from which infectious viral RNA can be produced [28] . This development facilitates the study of SARS-CoV gene functions and should promote the elucidation of function for ORFs whose function is still unknown [29] . Although it has been the perception that these ORFs are not essential for viral replication, they may play a role in the manifestation or severity of disease.