Sequence variations of Epstein-Barr virus LMP1 gene in gastric cancer and chronic gastritis isolates from Iranian patients

Abstract

Aim: The current study aimed to investigate sequence variations in the C-terminus of latent membrane protein 1 (LMP1) in Epstein-Barr virus (EBV) isolates from Iranian patients with chronic gastritis or gastric cancer (GC).

Background: LMP1, an essential viral oncoprotein, is the critical element in the immortalization of B cells. It contains a small twenty-four amino acid cytoplasmic N-terminal region, six transmembrane segments, and a two hundred amino acid cytoplasmic C-terminal domain. Most LMP1-mediated signal transduction events are moderated by some functional parts of the cytoplasmic C-terminal domain.

Methods: Thirty-two EBV-positive biopsy tissues were obtained from patients with gastric cancer and patients with chronic gastritis. The C-terminal nucleotide sequences of LMP1 were amplified using nested-PCR and analyzed by DNA sequencing.

Results: Four to eight copies of the 11 repeat elements (codon 254-302) were observed in the carboxyl-terminal site of patients, but no relationship was found between the number of repeat sequences and disease status. The 30-bp deletion corresponding to codon 345-354 of the B95-8 strain was observed in 34% of isolates, and the remaining samples were non-deleted. In the gastric cancer group, a higher number of 33-bp repeats (≥5 repeats) was observed in 30-bp-deletion (100%) than in non-deleted (42%) isolates, and the difference was statistically significant. Analysis revealed that a gastritis isolate may be the result of recombination between Alaskan and China1 strains.

Conclusion: Overall, the current results showed no association between C-terminal sequence variations of LMP1 and malignant or non-malignant isolate origin.

Keywords: EBV; Latent membrane protein 1; Repeat elements; Sequence variations.

Figure 1

Amino acid variation in the C-terminal of Iranian LMP1 isolates. Numbers across the top correspond to amino acid positions under which the B95-8 strain amino acid sequence is listed. The positions of the 33-bp repeats and the 30-bp deletion are denoted across the top, changes in the amino acids are denoted by letter changes, and a dash indicates a deletion of this amino acid position. Names in the left column refer to the individual isolates, and the capital letter GC represents a gastric cancer specimen, while the capital letter GA represents a gastritis specimen. The strain-identifying changes are shaded, patterned, and arranged by groups. Recombinant isolate is characterized by more than one strain identifying pattern and shading

Figure 2

Variations in the 11 aa repeat units in the C-terminal of LMP1 isolates obtained from biopsy tissues of gastric cancer and chronic gastritis patients. Across the top, the pattern of 11 aa repeat units between aa 253 and 306 in the LMP1 C-terminal domain of B95.8 strain is shown with the LMP1 amino acid positions. The names in the left column refer to the individual isolates. PQDPDNTDDNG, 11 aa repeat sequence; PQGPDNTDDNG, 11 aa repeat sequence with point mutation D→G; PHDPL, 5 amino acid sequence