The 57th amino acid conveys the differential subcellular localization of human immunodeficiency virus-1 Tat derived from subtype B and C

Genetic analysis of 37 cases with primary periodic paralysis in Chinese patients

BACKGROUND

Primary periodic paralysis (PPP) is an inherited disorders of ion channel dysfunction characterized by recurrent episodes of flaccid muscle weakness, which can classified as hypokalemic (HypoPP), normokalemic (NormoPP), or hyperkalemic (HyperPP) according to the potassium level during the paralytic attacks. However, PPP is charactered by remarkable clinical and genetic heterogeneity, and the diagnosis of suspected patients is based on the characteristic clinical presentation then confirmed by genetic testing. At present, there are only limited cohort studies on PPP in the Chinese population.

RESULTS

We included 37 patients with a clinical diagnosis of PPP. Eleven (29.7%) patients were tested using a specific gene panel and 26 (70.3%) by the whole-exome sequencing (WES). Twenty-two cases had a genetic variant identified, representing a diagnostic rate of 59.5% (22/37). All the identified mutations were either in the SCN4A or the CACNA1S gene. The overall detection rate was comparable between the panel (54.5%: 6/11) and WES (61.5%: 16/26). The remaining patients unresolved through panel sequencing were further analyzed by WES, without the detection of any mutation. The novel atypical splicing variant c.2020-5G > A affects the normal splicing of the SCN4A mRNA, which was confirmed by minigene splicing assay. Among 21 patients with HypoPP, 15 patients were classified as HypoPP-2 with SCN4A variants, and 6 HypoPP-1 patients had CACNA1S variants.

CONCLUSIONS

Our results suggest that SCN4A alleles are the main cause in our cohort, with the remainder caused by CACNA1S alleles, which are the predominant cause in Europe and the United States. Additionally, this study identified 3 novel SCN4A and 2 novel CACNA1S variants, broadening the mutation spectrum of genes associated with PPP.

The Signature Amino Acid Residue Serine 31 of HIV-1C Tat Potentiates an Activated Phenotype in Endothelial Cells

The natural cysteine to serine variation at position 31 of Tat in HIV-1C disrupts the dicysteine motif attenuating the chemokine function of Tat. We ask if there exists a trade-off in terms of a gain of function for HIV-1C Tat due to this natural variation. We constructed two Tat-expression vectors encoding Tat proteins discordant for the serine 31 residue (CS-Tat vs. CC-Tat), expressed the proteins in Jurkat cells under doxycycline control, and performed the whole transcriptome analysis to compare the early events of Tat-induced host gene expression. Our analysis delineated a significant enrichment of pathways and gene ontologies associated with the angiogenic signaling events in CS-Tat stable cells. Subsequently, we validated and compared angiogenic signaling events induced by CS- vs. CC-Tat using human umbilical vein endothelial cells (HUVEC) and the human cerebral microvascular endothelial cell line (hCMEC/D3). CS-Tat significantly enhanced the production of CCL2 from HUVEC and induced an activated phenotype in endothelial cells conferring on them enhanced migration, invasion, and in vitro morphogenesis potential. The ability of CS-Tat to induce the activated phenotype in endothelial cells could be of significance, especially in the context of HIV-associated cardiovascular and neuronal disorders. The findings from the present study are likely to help appreciate the functional significance of the SAR (signature amino acid residues) influencing the unique biological properties.

Lysine-specific demethylase 1 cooperates with BRAF-histone deacetylase complex 80 to enhance HIV-1 Tat-mediated transactivation

Despite the notable success of combination antiretroviral therapy, how to eradicate latent HIV-1 from reservoirs poses a challenge. The Tat protein plays an indispensable role in HIV reactivation and histone demethylase LSD1 promotes Tat-mediated long terminal repeats (LTR) activation. However, the role of LSD1 in remodeling chromatin and the role of its component BHC80 in activation of latent HIV-1 in T cells are unknown. Our findings indicate that LSD1 could decrease the level of histone H3 lysine 4 trimethylation (H3K4me3) at the HIV-1 promoter by recruiting histone lysine demethylase 5A (KDM5A) and preventing histone methyltransferase Set1A and WD-40 repeat protein 5 (WDR5) from binding to LTR. Moreover, BHC80 is necessary for LSD1-triggered LTR activation and assists LSD1 in activating LTR by binding to nucleotides 305-631 of LTR. In activated J-Lat-A2 cells, BHC80 expression was elevated and its isoform BHC80-6 promoted the association of BHC80 with LSD1. These results suggest that the LSD1-BHC80 complex enhances HIV-1 transcription by a decrease of H3K4me3 level at the viral promoter. Therefore, it might be used as a new drug target to reactivate latent HIV-1.

Cellular RelB interacts with the transactivator Tat and enhance HIV-1 expression

BACKGROUND

Human immunodeficiency virus type 1 (HIV-1) Tat protein plays an essential role in HIV-1 gene transcription. Tat transactivates HIV-1 long terminal repeat (LTR)-directed gene expression through direct interactions with the transactivation-responsive region (TAR) element and other cis elements in the LTR. The TAR-independent Tat-mediated LTR transactivation is modulated by several host factors, but the mechanism is not fully understood.

RESULTS

Here, we report that Tat interacts with the Rel homology domain of RelB through its core region. Furthermore, RelB significantly increases Tat-mediated transcription of the HIV-1 LTR and viral gene expression, which is independent of the TAR. Both Tat and RelB are recruited to the HIV-1 promoter, of which RelB facilitates the recruitment of Tat to the viral LTR. The NF-κB elements are key to the accumulation of Tat and RelB on the LTR. Knockout of RelB reduces the accumulation of RNA polymerase II on the LTR, and decreases HIV-1 gene transcription. Together, our data suggest that RelB contributes to HIV-1 transactivation.

CONCLUSIONS

Our results demonstrate that RelB interacts with Tat and enhances TAR-independent activation of HIV-1 LTR promoter, which adds new insights into the multi-layered mechanisms of Tat in regulating the gene expression of HIV-1.