scholarly journals p30 protein: a critical regulator of HTLV-1 viral latency and host immunity

Retrovirology ◽  
2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Ramona Moles ◽  
Sarkis Sarkis ◽  
Veronica Galli ◽  
Maria Omsland ◽  
Damian F. J. Purcell ◽  
...  
Keyword(s):  
T Cell ◽  
Viral Infection ◽  
Cell Transformation ◽  
Leukemia Virus ◽  
Single Point ◽  
Protein A ◽  
Indigenous Communities ◽  
Fine Tuning ◽  
Single Point Mutation ◽  
Subtype C

AbstractThe extraordinarily high prevalence of HTLV-1 subtype C (HTLV-1C) in some isolated indigenous communities in Oceania and the severity of the health conditions associated with the virus impress the great need for basic and translational research to prevent and treat HTLV-1 infection. The genome of the virus’s most common subtype, HTLV-1A, encodes structural, enzymatic, and regulatory proteins that contribute to viral persistence and pathogenesis. Among these is the p30 protein encoded by the doubly spliced Tax-orf II mRNA, a nuclear/nucleolar protein with both transcriptional and post-transcriptional activity. The p30 protein inhibits the productive replication cycle via nuclear retention of the mRNA that encodes for both the viral transcriptional trans-activator Tax, and the Rex proteins that regulate the transport of incompletely spliced viral mRNA to the cytoplasm. In myeloid cells, p30 inhibits the PU-1 transcription factor that regulates interferon expression and is a critical mediator of innate and adaptive immunity. Furthermore, p30 alters gene expression, cell cycle progression, and DNA damage responses in T-cells, raising the hypothesis that p30 may directly contribute to T cell transformation. By fine-tuning viral expression while also inhibiting host innate responses, p30 is likely essential for viral infection and persistence. This concept is supported by the finding that macaques, a natural host for the closely genetically related simian T-cell leukemia virus 1 (STLV-1), exposed to an HTLV-1 knockout for p30 expression by a single point mutation do not became infected unless reversion and selection of the wild type HTLV-1 genotype occurs. All together, these data suggest that inhibition of p30 may help to curb and eventually eradicate viral infection by exposing infected cells to an effective host immune response.

scholarly journals The Gfi-1 proto-oncoprotein contains a novel transcriptional repressor domain, SNAG, and inhibits G1 arrest induced by interleukin-2 withdrawal.

1996 ◽  
Vol 16 (11) ◽  
pp. 6263-6272 ◽  
Author(s):  
H L Grimes ◽  
T O Chan ◽  
P A Zweidler-McKay ◽  
B Tong ◽  
P N Tsichlis
Keyword(s):  
T Cell ◽  
T Cell Activation ◽  
Transcriptional Repression ◽  
Cell Activation ◽  
Cellular Proliferation ◽  
Single Point ◽  
Interleukin 2 ◽  
Transcriptional Repressor ◽  
Single Point Mutation ◽  
G1 Arrest

The Gfi-1 proto-oncogene is activated by provirus insertion in T-cell lymphoma lines selected for interleukin-2 (IL-2) independence in culture and in primary retrovirus-induced thymomas and encodes a nuclear, sequence-specific DNA-binding protein. Here we show that Gfi-1 is a position- and orientation-independent active transcriptional repressor, whose activity depends on a 20-amino-acid N-terminal repressor domain, coincident with a nuclear localization motif. The sequence of the Gfi-1 repressor domain is related to the sequence of the repressor domain of Gfi-1B, a Gfi-1-related protein, and to sequences at the N termini of the insulinoma-associated protein, IA-1, the homeobox protein Gsh-1, and the vertebrate but not the Drosophila members of the Snail-Slug protein family (Snail/Gfi-1, SNAG domain). Although not functionally characterized, these SNAG-related sequences are also likely to mediate transcriptional repression. Therefore, the Gfi-1 SNAG domain may be the prototype of a novel family of evolutionarily conserved repressor domains that operate in multiple cell lineages. Gfi-1 overexpression in IL-2-dependent T-cell lines allows the cells to escape from the G1 arrest induced by IL-2 withdrawal. Since a single point mutation in the SNAG domain (P2A) inhibits both the Gfi-1-mediated transcriptional repression and the G1 arrest induced by IL-2 starvation, we conclude that the latter depends on the repressor activity of the SNAG domain. Induction of Gfi-1 may therefore contribute to T-cell activation and tumor progression by repressing the expression of genes that inhibit cellular proliferation.

scholarly journals Identification of a new common provirus integration site in gross passage A murine leukemia virus-induced mouse thymoma DNA.

1987 ◽  
Vol 7 (1) ◽  
pp. 512-522 ◽  
Author(s):  
R Villemur ◽  
Y Monczak ◽  
E Rassart ◽  
C Kozak ◽  
P Jolicoeur
Keyword(s):  
T Cell ◽  
Murine Leukemia Virus ◽  
Cell Transformation ◽  
Integration Site ◽  
Leukemia Virus ◽  
Tumor Development ◽  
Mouse Strains ◽  
Mouse Tumor ◽  
Provirus Integration ◽  
Murine Leukemia

The Gross passage A murine leukemia virus (MuLV) induced T-cell leukemia of clonal (or oligoclonal) origin in inoculated mice. To study the role of the integrated proviruses in these tumor cells, we cloned several newly integrated proviruses (with their flanking cellular sequences) from a single tumor in procaryotic vectors. With each of the five clones obtained, a probe was prepared from the cellular sequences flanking the provirus. With one such probe (SS8), we screened several Gross passage A MuLV-induced SIM.S mouse tumor DNAs and found that, in 11 of 40 tumors, a provirus was integrated into a common region designated Gin-1. A 26-kilobase-pair sequence of Gin-1 was cloned from two lambda libraries, and a restriction map was derived. All proviruses were integrated as a cluster in the same orientation within a 5-kilobase-pair region of Gin-1, and most of them had a recombinant structure of the mink cell focus-forming virus type. The frequency of Gin-1 occupancy by provirus was much lower in thymoma induced by other strains of MuLV in other mouse strains. Using somatic-cell hybrid DNAs, we mapped Gin-1 on mouse chromosome 19. Gin-1 was not homologous to 16 known oncogenes and was distinct from the other common regions for provirus integration previously described. Therefore, Gin-1 appears to represent a new common provirus integration region. The integration of a provirus within Gin-1 might be an important event leading to T-cell transformation, and the Gin-1 region might harbor sequences which are involved in tumor development.

scholarly journals The Carboxy-Terminal Fragment of Nucleolin Interacts with the Nucleocapsid Domain of Retroviral Gag Proteins and Inhibits Virion Assembly

2000 ◽  
Vol 74 (23) ◽  
pp. 11027-11039 ◽  
Author(s):  
Eran Bacharach ◽  
Jason Gonsky ◽  
Kimona Alin ◽  
Marianna Orlova ◽  
Stephen P. Goff
Keyword(s):  
Leukemia Virus ◽  
Single Point ◽  
Host Protein ◽  
Single Point Mutation ◽  
Gag Protein ◽  
Virion Assembly ◽  
Gag Proteins ◽  
Carboxy Terminal

ABSTRACT A yeast two-hybrid screen for cellular proteins that interact with the murine leukemia virus (MuLV) Gag protein resulted in the identification of nucleolin, a host protein known to function in ribosome assembly. The interacting fusions contained the carboxy-terminal 212 amino acids of nucleolin [Nuc(212)]. The nucleocapsid (NC) portion of Gag was necessary and sufficient to mediate the binding to Nuc(212). The interaction of Gag with Nuc(212) could be demonstrated in vitro and was manifested in vivo by the NC-dependent incorporation of Nuc(212) inside MuLV virions. Overexpression of Nuc(212), but not full-length nucleolin, potently and specifically blocked MuLV virion assembly and/or release. A mutant of MuLV, selected to specifically disrupt the binding to Nuc(212), was found to be severely defective for virion assembly. This mutant harbors a single point mutation in capsid (CA) adjacent to the CA-NC junction, suggesting a role for this region in Moloney MuLV assembly. These experiments demonstrate that selection for proteins that bind assembly domain(s) can yield potent inhibitors of virion assembly. These experiments also raise the possibility that a nucleolin-Gag interaction may be involved in virion assembly.

scholarly journals Neoplastic transformation induced by an activated lymphocyte-specific protein tyrosine kinase (pp56lck).

1988 ◽  
Vol 8 (2) ◽  
pp. 540-550 ◽  
Author(s):  
J D Marth ◽  
J A Cooper ◽  
C S King ◽  
S F Ziegler ◽  
D A Tinker ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Cell Transformation ◽  
Single Point ◽  
Normal Growth ◽  
Protein Tyrosine Kinases ◽  
Single Point Mutation ◽  
Tyrosine Residue ◽  
Protein Tyrosine ◽  
Carboxy Terminal

The lck proto-oncogene encodes a lymphocyte-specific member of the src family of protein tyrosine kinases. Here we demonstrate that pp56lck is phosphorylated in vivo at a carboxy-terminal tyrosine residue (Tyr-505) analogous to Tyr-527 of pp60c-src. Substitution of phenylalanine for tyrosine at this position resulted in increased phosphorylation of a second tyrosine residue (Tyr-394) and was associated with an increase in apparent kinase activity. In addition, this single point mutation unmasked the oncogenic potential of pp56lck in NIH 3T3 cell transformation assays. Viewed in the context of similar results obtained with pp60c-src, it is likely that the enzymatic activity and transforming ability of all src-family protein tyrosine kinases can be regulated by carboxy-terminal tyrosine phosphorylation. We further demonstrate that overexpression of pp56lck in the murine T-cell lymphoma LSTRA as a result of a retroviral insertion event produces a kinase protein that despite wild-type primary structure is nevertheless hypophosphorylated at Tyr-505. Thus, control of normal growth in this lymphoid cell line may have been abrogated through acquisition of a posttranslationally activated version of pp56lck.

scholarly journals p53 functional impairment and high p21waf1/cip1 expression in human T- cell lymphotropic/leukemia virus type I-transformed T cells

Blood ◽  
1996 ◽  
Vol 88 (5) ◽  
pp. 1551-1560 ◽  
Author(s):  
A Cereseto ◽  
F Diella ◽  
JC Mulloy ◽  
A Cara ◽  
P Michieli ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Virus Type ◽  
Cell Transformation ◽  
Leukemia Virus ◽  
Type I ◽  
Wild Type ◽  
Human T Cell ◽  
Wild Type P53

Abstract Human T-cell lymphotropic/leukemia virus type I (HTLV-I) is associated with T-cell transformation both in vivo and in vitro. Although some of the mechanisms responsible for transformation remain unknown, increasing evidence supports a direct role of viral as well as dysregulated cellular proteins in transformation. We investigated the potential role of the tumor suppressor gene p53 and of the p53- regulated gene, p21waf1/cip1 (wild-type p53 activated fragment 1/cycling dependent kinases [cdks] interacting protein 1), in HTLV-I- infected T cells. We have found that the majority of HTLV-I-infected T cells have the wild-type p53 gene. However, its function in HTLV-I- transformed cells appears to be impaired, as shown by the lack of appropriate p53-mediated responses to ionizing radiation (IR). Interestingly, the expression of the p53 inducible gene, p21waf1/cip1, is elevated at the messenger ribonucleic acid and protein levels in all HTLV-I-infected T-cell lines examined as well as in Taxl-1, a human T- cell line stably expressing Tax. Additionally, Tax induces upregulation of a p21waf1/cip1 promoter-driven luciferase gene in p53 null cells, and increases p21waf1/cip1 expression in Jurkat T cells. These findings suggest that the Tax protein is at least partially responsible for the p53-independent expression of p21waf1/cip1 in HTLV-I-infected cells. Dysregulation of p53 and p21waf1/cip1 proteins regulating cell-cycle progression, may represent an important step in HTLV-I-induced T-cell transformation.

scholarly journals p53 functional impairment and high p21waf1/cip1 expression in human T- cell lymphotropic/leukemia virus type I-transformed T cells

Blood ◽  
1996 ◽  
Vol 88 (5) ◽  
pp. 1551-1560 ◽  
Author(s):  
A Cereseto ◽  
F Diella ◽  
JC Mulloy ◽  
A Cara ◽  
P Michieli ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Virus Type ◽  
Cell Transformation ◽  
Leukemia Virus ◽  
Type I ◽  
Wild Type ◽  
Human T Cell ◽  
Wild Type P53

Human T-cell lymphotropic/leukemia virus type I (HTLV-I) is associated with T-cell transformation both in vivo and in vitro. Although some of the mechanisms responsible for transformation remain unknown, increasing evidence supports a direct role of viral as well as dysregulated cellular proteins in transformation. We investigated the potential role of the tumor suppressor gene p53 and of the p53- regulated gene, p21waf1/cip1 (wild-type p53 activated fragment 1/cycling dependent kinases [cdks] interacting protein 1), in HTLV-I- infected T cells. We have found that the majority of HTLV-I-infected T cells have the wild-type p53 gene. However, its function in HTLV-I- transformed cells appears to be impaired, as shown by the lack of appropriate p53-mediated responses to ionizing radiation (IR). Interestingly, the expression of the p53 inducible gene, p21waf1/cip1, is elevated at the messenger ribonucleic acid and protein levels in all HTLV-I-infected T-cell lines examined as well as in Taxl-1, a human T- cell line stably expressing Tax. Additionally, Tax induces upregulation of a p21waf1/cip1 promoter-driven luciferase gene in p53 null cells, and increases p21waf1/cip1 expression in Jurkat T cells. These findings suggest that the Tax protein is at least partially responsible for the p53-independent expression of p21waf1/cip1 in HTLV-I-infected cells. Dysregulation of p53 and p21waf1/cip1 proteins regulating cell-cycle progression, may represent an important step in HTLV-I-induced T-cell transformation.

scholarly journals The SH3 Domain of Lck Modulates T-Cell Receptor-Dependent Activation of Extracellular Signal-Regulated Kinase through Activation of Raf-1

2007 ◽  
Vol 28 (2) ◽  
pp. 630-641 ◽  
Author(s):  
Manqing Li ◽  
Su Sien Ong ◽  
Bartek Rajwa ◽  
Vivian T. Thieu ◽  
Robert L. Geahlen ◽  
...  
Keyword(s):  
T Cell ◽  
Golgi Apparatus ◽  
Single Point ◽  
Cell Receptor ◽  
Single Point Mutation ◽  
Src Homology 3 ◽  
Extracellular Signal ◽  
Strong Stimulation ◽  
Src Homology 3 Domain ◽  
Src Homology

ABSTRACT Engagement of the T-cell antigen receptor (TCR) results in the proximal activation of the Src family tyrosine kinase Lck. The activation of Lck leads to the downstream activation of the Ras/Raf/MEK/ERK signaling pathway (where ERK is extracellular signal-related kinase). Under conditions of weak, but not strong, stimulation through the TCR, a version of Lck that contains a single point mutation in the SH3 (Src homology 3) domain (W97ALck) fails to support the activation of ERK, despite initiating signaling through the TCR, as demonstrated by the robust activation of ZAP-70, PLC-γ, and Ras. We determined that the signaling lesion in W97ALck-expressing cells lies at the level of Raf-1 activation and is dependent on the presence of tyrosines 340/341 in the Raf-1 sequence. These data demonstrate a second function for Lck in TCR-mediated signaling to ERK. Additionally, we found that a significant fraction of Lck is localized to the Golgi apparatus and that, compared with wild-type Lck, W97ALck displays aberrant Golgi membrane localization. Our results support a model where under conditions of weak stimulation through the TCR, in addition to activated Ras, Golgi apparatus-localized Lck is needed for the full activation of Raf-1.

Neoplastic transformation induced by an activated lymphocyte-specific protein tyrosine kinase (pp56lck)

1988 ◽  
Vol 8 (2) ◽  
pp. 540-550
Author(s):  
J D Marth ◽  
J A Cooper ◽  
C S King ◽  
S F Ziegler ◽  
D A Tinker ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Cell Transformation ◽  
Single Point ◽  
Normal Growth ◽  
Protein Tyrosine Kinases ◽  
Single Point Mutation ◽  
Tyrosine Residue ◽  
Protein Tyrosine ◽  
Carboxy Terminal

The lck proto-oncogene encodes a lymphocyte-specific member of the src family of protein tyrosine kinases. Here we demonstrate that pp56lck is phosphorylated in vivo at a carboxy-terminal tyrosine residue (Tyr-505) analogous to Tyr-527 of pp60c-src. Substitution of phenylalanine for tyrosine at this position resulted in increased phosphorylation of a second tyrosine residue (Tyr-394) and was associated with an increase in apparent kinase activity. In addition, this single point mutation unmasked the oncogenic potential of pp56lck in NIH 3T3 cell transformation assays. Viewed in the context of similar results obtained with pp60c-src, it is likely that the enzymatic activity and transforming ability of all src-family protein tyrosine kinases can be regulated by carboxy-terminal tyrosine phosphorylation. We further demonstrate that overexpression of pp56lck in the murine T-cell lymphoma LSTRA as a result of a retroviral insertion event produces a kinase protein that despite wild-type primary structure is nevertheless hypophosphorylated at Tyr-505. Thus, control of normal growth in this lymphoid cell line may have been abrogated through acquisition of a posttranslationally activated version of pp56lck.

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