Tetrahymena telomerase holoenzyme subunits p75, p45 and p19 form a subcomplex (7–4–1) peripheral to the catalytic core. We report structures of p45 and p19 and reveal them as the Stn1 and Ten1 subunits of the CST complex, which stimulates telomerase complementary-strand synthesis. 7–4–1 binds telomeric single-stranded DNA, and mutant p19 overexpression causes telomere 3′-overhang elongation. We propose that telomerase-tethered Tetrahymena CST coordinates telomere G-strand and C-strand synthesis.
Summary
Despite of important functions of strigolactones (SLs) and karrikins (KARs) in plant development, plant–parasite and plant–fungi interactions, their roles in soybean–rhizobia interaction remain elusive. SL/KAR signaling genes GmMAX2a, GmD14s, and GmKAIs are activated by rhizobia infection. GmMAX2a restored atmax2 root hair defects and soybean root hairs were changed in GmMAX2a overexpression (GmMAX2a‐OE) or knockdown (GmMAX2a‐KD) mutants. GmMAX2a‐KD gave fewer, whereas GmMAX2a‐OE produced more nodules than GUS hairy roots. Mutation of GmMAX2a in its KD or OE transgenic hairy roots affected the rhizobia infection‐induced increases in early nodulation gene expression. Both mutant hairy roots also displayed the altered auxin, jasmonate and abscisic acid levels, as further verified by transcriptomic analyses of their synthetic genes. Overexpression of an auxin synthetic gene GmYUC2a also affected SL and KAR signaling genes. GmMAX2a physically interacted with SL/KAR receptors GmD14s, GmKAIs, and GmD14Ls with different binding affinities, depending on variations in the critical amino acids, forming active D14/KAI‐SCFMAX2 complexes. The knockdown mutant roots of the nodule‐specifically expressing GmKAIs and GmD14Ls gave fewer nodules, with altered expression of several early nodulation genes. The expression levels of GmKAIs, and GmD14Ls were markedly changed in GmMAX2a mutant roots, so did their target repressor genes GmD53s and GmSMAX1s. Thus, SL and KAR signaling were involved in soybean–rhizobia interaction and nodulation partly through interactions with hormones, and this may explain the different effects of MXA2 orthologs on legume determinate and indeterminate nodulation. The study provides fresh insights into the roles of GmMAX2‐mediated SL/KAR signaling in soybean root hair and nodule formation.
The amino acid DL-lysine has been investigated using the surface-sensitive probe XPS (x-ray photoelectron spectroscopy). The XPS data confirm that solid-state lysine exists in the zwitterionic form. However, during the course of x-ray irradiation in the experiment, the molecule was observed to decompose. A decomposition mechanism consistent with the data has been proposed which involves transformation of the zwitterion to a free base, followed by decarboxylation, to produce 1,5-diaminopentane and CO2 gas. It would appear that caution should be exerted when studying amino acids using XPS if long x-ray irradiation times are employed.
Background
Analysis of viral protein–protein interactions is an essential step to uncover the viral protein functions and the molecular mechanism for the assembly of a viral protein complex. We employed a mammalian two-hybrid system to screen all the viral proteins of SARS-CoV-2 for the protein–protein interactions.
Results
Our study detected 48 interactions, 14 of which were firstly reported here. Unlike Nsp1 of SARS-CoV, Nsp1 of SARS-CoV-2 has the most interacting partners among all the viral proteins and likely functions as a hub for the viral proteins. Five self-interactions were confirmed, and five interactions, Nsp1/Nsp3.1, Nsp3.1/N, Nsp3.2/Nsp12, Nsp10/Nsp14, and Nsp10/Nsp16, were determined to be positive bidirectionally. Using the replicon reporter system of SARS-CoV-2, we screened all viral Nsps for their impacts on the viral replication and revealed Nsp3.1, the N-terminus of Nsp3, significantly inhibited the replicon reporter gene expression. We found Nsp3 interacted with N through its acidic region at N-terminus, while N interacted with Nsp3 through its NTD, which is rich in the basic amino acids. Furthermore, using purified truncated N and Nsp3 proteins, we determined the direct interactions between Nsp3 and N protein.
Conclusions
Our findings provided a basis for understanding the functions of coronavirus proteins and supported the potential of interactions as the target for antiviral drug development.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.