FIG. 4.

Northern blot analysis detects more than one ICP0 intron-bearing transcript in KOS1.1-infected HeLa cells, and their accumulation requires ICP27. (A) Schematic diagram of the HSV-1 ICP0 gene. Exon sequences are indicated by filled boxes, and introns are marked by dashed lines. Positions of the mRNA start site, ATG start codon, TAA stop codon, 5′ and 3′ untranslated regions, and the poly(A) cleavage site are shown. The fragments specific for upstream sequences, intron 1 sequences, and exon plus intron sequences that were used to prepare radiolabeled probes for Northern blot analysis are indicated by hatched bars. (B) Total RNA or poly(A)⁺ RNA was prepared from mock-infected, KOS1.1-infected, or d27-1-infected HeLa cells at 6 h postinfection. Northern blot analysis was conducted using the intron-specific probe (right), and then the membrane was reprobed with the exon/intron probe (left). Transcripts were given the designations a to f for ease of description in the text. M, RNA size markers in kilobases. (C) Northern blot of total RNA from mock-infected, KOS1.1-infected, or d27-1-infected HeLa cells using the ICP0 intron 1 strand-specific riboprobe. (D) Northern blot of total RNA from mock-infected or KOS1.1-infected HeLa cells using the upstream probe (left) and the intron 1 probe (right).