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Articles by Jingjing Li
Total Records ( 3 ) for Jingjing Li
  Yuxian He , Jianwei Cheng , Jingjing Li , Zhi Qi , Hong Lu , Mingxin Dong , Shibo Jiang and Qiuyun Dai
  Human immunodeficiency virus type 1 (HIV-1) entry into the host cell involves a cascade of events and currently represents one of most attractive targets in the search for new antiviral drugs. The fusion-active gp41 core structure is a stable six-helix bundle (6-HB) folded by its trimeric N-terminal heptad repeat (NHR) and C-terminal heptad repeat (CHR). Peptides derived from the CHR region of HIV-1 gp41 are potent fusion inhibitors that target the NHR to block viral and cellular membrane fusion in a dominant negative fashion. However, all CHR peptides reported to date are derived primarily from residues 628 to 673 of gp41; little attention has been paid to the upstream sequence of the pocket binding domain (PBD) in the CHR. Here, we have identified a motif (621QIWNNMT627) located at the upstream region of the gp41 CHR, immediately adjacent to the PBD (628WMEWEREI635). Biophysical characterization demonstrated that this motif is critical for the stabilization of the gp41 6-HB core. The peptide CP621-652, containing the 621QIWNNMT627 motif, was able to interact with T21, a counterpart peptide derived from the NHR, to form a typical 6-HB structure with a high thermostability (thermal unfolding transition [Tm] value of 82°C). In contrast, the 6-HB formed by the peptides N36 and C34, which has been considered to be a core structure of the fusion-active gp41, had a Tm of 64°C. Different from T-20 (brand name Fuseon), which is the first and only HIV-1 fusion inhibitor approved for clinical use, CP621-652 could efficiently block 6-HB formation in a dose-dependent manner. Significantly, CP621-652 had potent inhibitory activity against HIV-1-mediated cell-cell fusion and infection, especially against T-20- and C34-resistant virus. Therefore, our works provide important information for understanding the core structure of the fusion-active gp41 and for designing novel anti-HIV peptides.
  Yuxian He , Shuwen Liu , Jingjing Li , Hong Lu , Zhi Qi , Zhonghua Liu , Asim K. Debnath and Shibo Jiang
  The fusogenic human immunodeficiency virus type 1 (HIV-1) gp41 core structure is a stable six-helix bundle formed by its N- and C-terminal heptad repeat sequences. Notably, the negatively charged residue Asp632 located at the pocket-binding motif in the C-terminal heptad repeat interacts with the positively charged residue Lys574 in the pocket formation region of the N-terminal heptad repeat to form a salt bridge. We previously demonstrated that the residue Lys574 plays an essential role in six-helix bundle formation and virus infectivity and is a key determinant of the target for anti-HIV fusion inhibitors. In this study, the functionality of residue Asp632 has been specifically characterized by mutational analysis and biophysical approaches. We show that Asp632 substitutions with positively charged residues (D632K and D632R) or a hydrophobic residue (D632V) could completely abolish Env-mediated viral entry, while a protein with a conserved substitution (D632E) retained its activity. Similar to the Lys574 mutations, nonconserved substitutions of Asp632 also severely impaired the α-helicity, stability, and conformation of six-helix bundles as shown by N36 and C34 peptides as a model system. Furthermore, nonconserved substitutions of Asp632 significantly reduced the potency of C34 to sequestrate six-helix bundle formation and to inhibit HIV-1-mediated cell-cell fusion and infection, suggesting its importance for designing antiviral fusion inhibitors. Taken together, these data suggest that the salt bridge between the N- and C-terminal heptad repeat regions of the fusion-active HIV-1 gp41 core structure is critical for viral entry and inhibition.
  Mei Zhu , Fengsong Wang , Feng Yan , Phil Y. Yao , Jian Du , Xinjiao Gao , Xiwei Wang , Quan Wu , Tarsha Ward , Jingjing Li , Steve Kioko , Renming Hu , Wei Xie , Xia Ding and Xuebiao Yao
  Chromosome segregation in mitosis is orchestrated by dynamic interaction between spindle microtubules and the kinetochore. Septin (SEPT) belongs to a conserved family of polymerizing GTPases localized to the metaphase spindle during mitosis. Previous study showed that SEPT2 depletion results in chromosome mis-segregation correlated with a loss of centromere-associated protein E (CENP-E) from the kinetochores of congressing chromosomes (1). However, it has remained elusive as to whether CENP-E physically interacts with SEPT and how this interaction orchestrates chromosome segregation in mitosis. Here we show that SEPT7 is required for a stable kinetochore localization of CENP-E in HeLa and MDCK cells. SEPT7 stabilizes the kinetochore association of CENP-E by directly interacting with its C-terminal domain. The region of SEPT7 binding to CENP-E was mapped to its C-terminal domain by glutathione S-transferase pull-down and yeast two-hybrid assays. Immunofluorescence study shows that SEPT7 filaments distribute along the mitotic spindle and terminate at the kinetochore marked by CENP-E. Remarkably, suppression of synthesis of SEPT7 by small interfering RNA abrogated the localization of CENP-E to the kinetochore and caused aberrant chromosome segregation. These mitotic defects and kinetochore localization of CENP-E can be successfully rescued by introducing exogenous GFP-SEPT7 into the SEPT7-depleted cells. These SEPT7-suppressed cells display reduced tension at kinetochores of bi-orientated chromosomes and activated mitotic spindle checkpoint marked by Mad2 and BubR1 labelings on these misaligned chromosomes. These findings reveal a key role for the SEPT7-CENP-E interaction in the distribution of CENP-E to the kinetochore and achieving chromosome alignment. We propose that SEPT7 forms a link between kinetochore distribution of CENP-E and the mitotic spindle checkpoint.
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