Post-translational modifications of hnRNP A1 differentially modulate retroviral IRES-mediated translation initiation

Abstract

The full-length mRNAs of the human immunodeficiency virus type-1 (HIV-1), the human T-cell lymphotropic virus type-1 (HTLV-1), and the mouse mammary tumor virus (MMTV) harbor IRESs. The activity of the retroviral-IRESs requires IRES-transacting factors (ITAFs), being hnRNP A1, a known ITAF for the HIV-1 IRES. In this study, we show that hnRNP A1 is also an ITAF for the HTLV-1 and MMTV IRESs. The MMTV IRES proved to be more responsive to hnRNP A1 than either the HTLV-1 or the HIV-1 IRESs. The impact of post-translational modifications of hnRNP A1 on HIV-1, HTLV-1 and MMTV IRES activity was also assessed. Results show that the HIV-1 and HTLV-1 IRESs were equally responsive to hnRNP A1 and its phosphorylation mutants S4A/S6A, S4D/S6D and S199A/D. However, the S4D/S6D mutant stimulated the activity from the MMTV-IRES to levels significantly higher than the wild type hnRNP A1. PRMT5-induced symmetrical di-methylation of arginine residues of hnRNP A1 enabled the ITAF to stimulate the HIV-1 and HTLV-1 IRESs while reducing the stimulatory ability of the ITAF over the MMTV IRES. We conclude that retroviral IRES activity is not only dependent on the recruited ITAFs but also relies on how these proteins are modified at the post-translational level.

Arginine methylation of SARS-Cov-2 nucleocapsid protein regulates RNA binding, its ability to suppress stress granule formation, and viral replication

“…For example, the arginine methylation of HIV Tat protein decreases its transactivation function [ 43 ]. The inhibition of PRMT5 prevents host hnRNPA1 RGG/RG motif methylation and inhibits HIV-1 and HTLV-1 IRES function [ 44 ]. Moreover, PRMT5 methylates hepatitis B virus core (HBc) protein within its C-terminal arginine-rich domain to regulate its cellular localization [ 45 ].…”

The double-stranded RNA-binding protein, Staufen1, is an IRES-transacting factor regulating HIV-1 cap-independent translation initiation

“…For this, HEK 293T cell lines were transfected with the pNL-4.3-RLuc DNA (Figure 1C , upper panel), which has a hemagglutinin (HA)-tagged Renilla luciferase (RLuc-HA) reporter gene inserted in frame with the Gag-protein start codon, generating a Gag-RLuc-HA fusion protein ( 57 ). This plasmid allows a direct evaluation of Gag synthesis from the HIV-1 vRNA, using the Gag-RLuc-HA reporter and its luciferase activity as a readout ( 25 , 57 , 69 , 73 ). HEK 293T cells were cotransfected with the pNL-4.3-RLuc plasmid and a short interfering RNA (siRNA) si55/63 (50 nM) targeting Staufen1 mRNAs ( 31 , 32 ) or a non-related scrambled control siRNA (scRNA; 50 nM).…”

“…Western blots were visualized by enhanced luminescence by a chemiluminescence reaction using 4-hydroxycinnamic acid (#800237, Merck) and luminol (#09253, Sigma-Aldrich), the SuperSignal™ West Femto Maximum Sensitivity Substrate (#34096, Thermo Fisher Scientific Inc.) or Western Lightning Plus-ECL (# NEL 121001, PerkinElmer Health Science Canada, Inc, Ontario, Canada). The western blot films (Fuji medical X-ray film Super HR-U 30 or Hyblot CL (# DV-3012, Denville Scientific Inc., NJ, USA)) were digitized using a CanonScan 9950F scanner, or membrane chemiluminescence was captured using an Alliance 2.7 imaging system (UVItec Cambridge, Topac Inc., 231 CJC Highway, Cohasset, MA, USA) as in ( 69 ).…”

HBx represses WDR77 to enhance HBV replication by DDB1-mediated WDR77 degradation in the liver

“…Our finding suggests that WDR77 is able to restrict the cccDNA transcription in the cells. PRMT5 has been reported to implicate in the regulation of viral replication and pathogenesis by targeting a variety of cellular substrates and viral proteins in a methyltransferase activity-dependent manner, such as HBV replication, bovine leukemia virus (BLV) infection, the human immunodeficiency virus type-1 (HIV-1) replication, the human T-cell lymphotropic virus type-1 (HTLV-1) replication, and the mouse mammary tumor virus (MMTV) replication and RNA/DNA virus infection 42 - 44 . However, whether WDR77 is involved in other viral regulation through modulating the activity of PRMT5 has not been reported.…”