Expression of alternatively spliced human T-lymphotropic virus type I pX mRNA in infected cell lines and in primary uncultured cells from patients with adult T-cell leukemia/lymphoma and healthy carriers.

Abstract

Although human T-cell lymphotropic virus type I (HTLV-I) is the etiologic agent of adult T-cell leukemia/lymphoma (ATL), the role of viral gene expression in the progression to and maintenance of the leukemic state in vivo is unclear because of the inability of most previous studies to readily detect HTLV-I RNA in infected individuals. By using the reverse transcriptase-polymerase chain reaction, we detected spliced messages for the HTLV-I pX regulatory genes in primary uncultured cells from ATL patients and healthy asymptomatic carriers. In addition to the expected doubly spliced pX message, three alternatively spliced mRNAs were demonstrated (pXA17, pX-p21rex, and pX-orflI mRNAs, where orf = open reading frame). The same splice sites were shown in the messages from uncultured ATL cells and from the HTLV-I-producing C1O/MJ cell line. Alternatively spliced pX mRNAs have the potential to code for known and putative pX gene products. Among the transcripts is a monocistronic mRNA likely to code for p2l'rx (pX-p2lrx mRNA). Since alternative splicing of HTLV

Titration of cellular export factors, but not heteromultimerization, is the molecular mechanism of trans-dominant HTLV-1 Rex mutants

“…However, since overexpression of Rexp21 was essential for the inhibition of Rev, especially if compared to the highly TD mutant RevM10, we suggest that cotransfection of higher amounts of Rex 2 would also result in Rev inhibition. Rexp21, which is generated by alternative splicing, was also detected in primary uncultured ATL leukemia cells (Berneman et al, 1992). Considering the TD potential of p21Rex it might play a functional role in regulating HTLV-1 gene expression, e.g., during the maintenance of the long latency period observed in HTLV-1 infected carriers.…”

“…Since the natural occurring splice variant Rexp21 (Berneman et al, 1992;Bhat et al, 1993;Orita et al, 1991) was reported to be transdominant (Kubota et al, 1996) we constructed a Rexp21-GFP hybrid protein. Rexp21 is lacking the ®rst 78 N-terminal amino acids, including the RNAbinding domain and the nuclear localization signal (NLS).…”

Mitochondrial Alterations Induced by the p13II Protein of Human T-cell Leukemia Virus Type 1

“…To gain further insight into the mechanisms governing HTLV-1 replication and pathogenesis, a number of studies are currently focusing on recently described "accessory" proteins encoded in ORFs x-I and x-II, which are located in a 3Ј portion of the viral genome termed the X region (3)(4)(5). Although the accessory ORFs are dispensable for virus propagation and immortalization of T-cells in vitro (6 -8), they are essential for efficient viral propagation in animal models (9 -11).…”

The human T-cell leukemia virus type 1 p13II protein: effects on mitochondrial function and cell growth

“…18,19 p13 II corresponds to the carboxy-terminal 87 amino acids of p30 II and is produced from a singly spliced mRNA that lacks the Tax initiator codon. 20,21 p13 II also lacks the NLS sequence of p30 II , and is predominantly mitochondrial, 22 although it can occasionally be detected in the nucleus, 14 especially when expressed at high levels (our unpublished observations). Mitochondrial accumulation of p13 II has been documented in a variety of cell types, including T cells, the natural target of HTLV-1 infection (Figure 2).…”

“…In this study, the p13 II mRNA was detected in two out of three IL-2-dependent HTLV-1-infected cell lines, 4/4 IL-2-independent infected cell lines, and in 6/10 ATLL patients, but in 0/3 healthy HTLV-1 carriers. 21 These observations suggest that the expression of p13 II might be more prominent during the course of disease development than in asymptomatic infection. This could reflect higher expression levels in individual cells or increased numbers of infected cells at later stages of disease, possibilities that could be explored by measuring viral DNA loads versus p13 II mRNA.…”