DING Proteins from Phylogenetically Different Species Share High Degrees of Sequence and Structure Homology and Block Transcription of HIV-1 LTR Promoter

Abstract

Independent research groups reported that DING protein homologues isolated from bacterial, plant and human cells demonstrate the anti-HIV-1 activity. This might indicate that diverse organisms utilize a DING-mediated broad-range protective innate immunity response to pathogen invasion, and that this mechanism is effective also against HIV-1. We performed structural analyses and evaluated the anti-HIV-1 activity for four DING protein homologues isolated from different species. Our data show that bacterial PfluDING, plant p38SJ (pDING), human phosphate binding protein (HPBP) and human extracellular DING from CD4 T cells (X-DING-CD4) share high degrees of structure and sequence homology. According to earlier reports on the anti-HIV-1 activity of pDING and X-DING-CD4, other members of this protein family from bacteria and humans were able to block transcription of HIV-1 and replication of virus in cell based assays. The efficacy studies for DING-mediated HIV-1 LTR and HIV-1 replication blocking activity showed that the LTR transcription inhibitory concentration 50 (IC50) values ranged from 0.052–0.449 ng/ml; and the HIV-1 replication IC50 values ranged from 0.075–0.311 ng/ml. Treatment of cells with DING protein alters the interaction between p65-NF-κB and HIV-1 LTR. Our data suggest that DING proteins may be part of an innate immunity defense against pathogen invasion; the conserved structure and activity makes them appealing candidates for development of a novel therapeutics targeting HIV-1 transcription.

Human X‐DING‐CD4 mediates resistance to HIV‐1 infection through novel paracrine‐like signaling

“…Because phosphorylation of NF‐κB subunits is indispensable for its nuclear function , the depletion of these forms from the nuclear compartment leads to disruption of transcription. Consequently, because the X‐DING was found in the nuclear compartment (not shown), we surmise that blockage of HIV‐1 LTR transcription is related to dephosphorylation of NF‐κB mediated by the nuclear X‐DING. Further investigations will determine the X‐DING amino acid motifs regulating this function.…”

“…We reported previously that exposure of cells to exogenous form of X‐DING protein blocked binding of NF‐κB to the HIV‐1 LTR in the nucleus , suggesting that the interaction of this soluble factor with the membrane of bystander cell affected events in the nuclear compartment. To determine the nature of these X‐DING cell membrane interactions, we employed an HIV‐1 susceptible 1G5 indicator cell line expressing the luciferase gene under the control of the HIV‐1 LTR , the ultimate target of X‐DING activity.…”

“…An earlier study showed that the X‐DING protein interfered with NF‐κB/LTR binding and this process was particularly efficient before the NF‐κB formed a complex with the cognate sequence of DNA probe . This result suggested that X‐DING incapacitated the nuclear NF‐κB‐DNA binding mediated by the phosphorylated p50 subunit of the p50/p65 dimer .…”

The Dichotomy of the Poly(ADP-Ribose) Polymerase-Like Thermozyme from Sulfolobus solfataricus

“…It is worth noting that independent research groups reported that DING protein homologues isolated from bacterial, plant and human cells demonstrate the anti-HIV-1 activity [40]. Bacterial PfluDING, plant p38SJ (pDING), human phosphate binding protein (HPBP), and human extracellular DING from CD4 T cells (X-DING-CD4) were able to block transcription of HIV-1 and replication of virus in cell based assays.…”

“…Transcription of HIV-1 depends on NF-kB, involved in the immediate signaling mechanisms of the innate immunity responses against infecting pathogens, including HIV-1. Therefore, the anti-NF-kB activity of DING proteins is of particular interest and might indicate that diverse organisms utilize a DING-mediated broad-range protective innate immunity response to pathogen invasion, and that this mechanism is effective also against HIV-1 [40].…”