Drug 9AA reactivates p21/Waf1 and Inhibits HIV-1 progeny formation.

It has been demonstrated that the p53 pathway plays an important role in HIV-1 infection. Previous work from our lab has established a model demonstrating how p53 could become inactivated in HIV-1 infected cells through binding to Tat. Subsequently, p53 was inactivated and lost its ability to transactivate its downstream target gene p21/waf1. P21/waf1 is a well-known cdk inhibitor (CKI) that can lead to cell cycle arrest upon DNA damage. Most recently, the p21/waf1 function was further investigated as a molecular barrier for HIV-1 infection of stem cells. Therefore, we reason that the restoration of the p53 and p21/waf1 pathways could be a possible theraputical arsenal for combating HIV-1 infection. In this current study, we show that a small chemical molecule, 9-aminoacridine (9AA) at low concentrations, could efficiently reactivate p53 pathway and thereby restoring the p21/waf1 function. Further, we show that the 9AA could significantly inhibit virus replication in activated PBMCs, likely through a mechanism of inhibiting the viral replication machinery. A mechanism study reveals that the phosphorylated p53ser15 may be dissociated from binding to HIV-1 Tat protein, thereby activating the p21/waf1 gene. Finally, we also show that the 9AA-activated p21/waf1 is recruited to HIV-1 preintegration complex, through a mechanism yet to be elucidated.

The sarcoglycan complex in Schwann cells and its role in myelin stability.

Sarcoglycans are originally identified in muscle for their involvement in limb-girdle muscular dystrophies. They form a multi-meric complex (alpha-, beta-, gamma-, delta-sarcoglycan) that associates with dystrophin, dystroglycan and other proteins to constitute the larger dystrophin-glycoprotein complex at the muscle membrane. Three sarcoglycan subunits (epsilon-, beta-, delta-sarcoglycan) were previously identified in Schwann cells and shown to associate with dystroglycan and a Schwann cell-specific dystrophin isoform (Dp116) at the outermost Schwann cell membrane. Currently, little is known about the exact composition and function of the sarcoglycan complex in the peripheral nervous system. In this study, we showed that the Schwann cell sarcoglycan complex consists of epsilon-, beta-, delta-sarcoglycan and the newly identified zeta-sarcoglycan subunit. The expression of sarcoglycans precedes the onset of myelination and is induced by neurons. In sarcoglycan-deficient BIO14.6 hamsters, loss of the Schwann cell sarcoglycan complex reduces the steady state levels of alpha-dystroglycan and Dp116. Ultrastructural analysis of sciatic nerves from the mutant animals revealed altered myelin sheaths and disorganized Schmidt-Lanterman incisures indicative of myelin instability. The disruption in myelin structure increased in severity with age. Nerve conduction studies also showed subtle electrophysiological abnormalities in the BIO14.6 hamsters consistent with reduced myelin stability. Together, these findings suggest an important role of sarcoglycans in the stability of peripheral nerve myelin.

The puromycin-sensitive aminopeptidase PAM-1 is required for meiotic exit and anteroposterior polarity in the one-cell Caenorhabditis elegans embryo.

In the nematode Caenorhabditis elegans, sperm entry into the oocyte triggers the completion of meiosis and the establishment of the embryonic anteroposterior (AP) axis. How the early embryo makes the transition from a meiotic to a mitotic zygote and coordinates cell cycle changes with axis formation remains unclear. We have discovered roles for the C. elegans puromycin-sensitive aminopeptidase PAM-1 in both cell cycle progression and AP axis formation, further implicating proteolytic regulation in these processes. pam-1 mutant embryos exhibit a delay in exit from meiosis: thus, this peptidase is required for progression to mitotic interphase. In addition, the centrosomes associated with the sperm pronucleus fail to closely associate with the posterior cortex in pam-1 mutants, and the AP axis is not specified. The meiotic exit and polarity defects are separable, as inactivation of the B-type cyclin CYB-3 in pam-1 mutants rescues the meiotic exit delay but not the polarity defects. Thus PAM-1 may regulate CYB-3 during meiotic exit but presumably targets other protein(s) to regulate polarity. We also show that the pam-1 gene is expressed both maternally and paternally, providing additional evidence that sperm-donated gene products have important roles during early embryogenesis in C. elegans. The degradation of proteins through ubiquitin-mediated proteolysis has been previously shown to regulate the cell cycle and AP axis formation in the C. elegans zygote. Our analysis of PAM-1 requirements shows that a puromycin-sensitive aminopeptidase is also required for proteolytic regulation of the oocyte to embryo transition.