Tyrosine sulfate trapped by amber

Histone tyrosine sulfation by SULT1B1 regulates H4R3me2a and gene transcription

Tyrosine sulfation is a common posttranslational modification in mammals. To date, it has been thought to be limited to secreted and transmembrane proteins, but little is known about tyrosine sulfation on nuclear proteins. Here we report that SULT1B1 is a histone sulfotransferase that can sulfate the tyrosine 99 residue of nascent histone H3 in cytosol. The sulfated histone H3 can be transported into the nucleus and majorly deposited in the promoter regions of genes in chromatin. While the H3Y99 residue is buried inside octameric nucleosome, dynamically regulated subnucleosomal structures provide chromatin-H3Y99sulf the opportunity of being recognized and bound by PRMT1, which deposits H4R3me2a in chromatin. Disruption of H3Y99sulf reduces PRMT1 binding to chromatin, H4R3me2a level and gene transcription. These findings reveal the mechanisms underlying H3Y99 sulfation and its cross-talk with H4R3me2a to regulate gene transcription. This study extends the spectrum of tyrosine sulfation on nuclear proteins and the repertoire of histone modifications regulating chromatin functions.

A double-mimetic peptide efficiently neutralizes HIV-1 by bridging the CD4- and coreceptor-binding sites of gp120

The HIV-1 envelope glycoprotein binds cooperatively to its cellular receptor CD4 and a coreceptor, principally CXCR4 or CCR5. We have previously improved a natural amino-acid form of a scorpion toxin-derived CD4-mimetic peptide and in parallel generated sulfopeptide mimetics of the CCR5 amino terminus. Here we show that some fusions of these CCR5- and CD4-mimetic peptides, expressed as immunoadhesins, neutralize HIV-1 more efficiently than CD4-Fc or equimolar mixtures of immunoadhesin forms of each peptide. Specifically, double-mimetic peptides with linkers of 11 amino acids or greater, and with the CCR5-mimetic component preceding the CD4-mimetic component, were more efficient than constructs with shorter linkers or in a reverse orientation. The potency of these constructs derives from (i) their ability to simultaneously and cooperatively bind the CD4- and CCR5-binding sites of a single gp120 monomer of the HIV-1 envelope glycoprotein trimer and (ii) the ability of the CCR5-mimetic component to prevent the CD4-mimetic peptide from promoting infection when cellular CD4 is limiting. Thus, there is a significant advantage to simultaneously targeting both conserved regions of the HIV-1 envelope glycoprotein.

IMPORTANCE

This report describes a novel class of peptides that potently inhibit HIV-1 entry. These peptides simultaneously target the receptor- and coreceptor-binding sites of the HIV-1 envelope glycoprotein gp120. Peptides of this class overcome key limitations of inhibitors that target only one gp120 binding region and illustrate the utility of binding the sulfotyrosine-binding pockets of gp120.

A tyrosine-sulfated CCR5-mimetic peptide promotes conformational transitions in the HIV-1 envelope glycoprotein

The HIV-1 envelope glycoprotein is a trimeric complex of heterodimers composed of a surface glycoprotein, gp120, and a transmembrane component, gp41. The association of this complex with CD4 stabilizes the coreceptor-binding site of gp120 and promotes the exposure of the gp41 helical region 1 (HR1). Here, we show that a 15-amino-acid peptide mimetic of the HIV-1 coreceptor CCR5 fused to a dimeric antibody Fc domain (CCR5mim-Ig) bound two gp120 molecules per envelope glycoprotein complex and by itself promoted HR1 exposure. CCR5mim-Ig also stabilized the association of a CD4-mimetic peptide with the envelope glycoprotein. A fusion of the CD4- and CCR5-mimetic peptides, DM1, bound gp120 and neutralized R5, R5X4, and X4 HIV-1 isolates comparably to CD4, and they did so markedly more efficiently than either peptide alone. Our data indicate that the potency of DM1-Ig derives from its avidity for the HIV-1 envelope glycoprotein trimer and from the bidirectional induction of its receptor-mimetic components. DM1 has significant advantages over other inhibitors that target both coreceptor and CD4-binding sites, and it may serve as a lead for a new class of HIV-1 inhibitor peptides.