ICP27 IMMEDIATE-EARLY GENE, GLYCOPROTEIN-K (GK) AND DNA HELICASE HOMOLOGS OF INFECTIOUS LARYNGOTRACHEITIS VIRUS (GALLID HERPESVIRUS-1) SA-2STRAIN

A 4.8 kilobase segment located at the left-terminal in the unique long (U-L) region of infectious laryngotracheitis virus (ILTV) SA-2 strain contained three open reading frames (ORFs). The first of 421 amino ac ids (aa) was located at map units 0.065 to 0.07, and its predicted 48 kiloDaltons (kDa) protein product has significant homology to the imme diate early regulatory protein ICP27 (UL54) of herpes simplex virus ty pe-1 (HSV-1), to varicella-zoster virus (VZV) ORF4 and to equine herpe svirus 1 (EHV-1) ORF5. The zinc finger conserved in the C-terminal of the proteins from HSV-1, VZV and EHV-1, is poorly conserved in ILTV ho mologue. The second ORF of 336 aa, located at map units 0.075 to 0.08, has a predicted molecular weight (MW) of 38 kDa with significant homo logy to glycoprotein K (gK) of HSV-1 (UL53), ORF5 of VZV and ORF6 of E HV-1. ILTV gK has features characteristic of a membrane-bound glycopro tein. The 3' region of a third ORF was located at map units 0.08 to 0. 095. Translation of the sequence revealed significant homology to the 3'-region of the DNA helicase-primase complex protein (UL52) of HSV-1, ORF6 of VZV and ORF 7 of EHV-1. Northern blot analyses were used to c haracterize the ILTV ICP27, gK and DNA helicase mRNAs. The data reveal ed that ILTV ICP27 is an immediate early gene that encodes a 1.6 kb mR NA, ILTV gK encodes a late transcript of 1.8 kb, while ILTV DNA helica se encodes a late transcript of 3.7 kb.