Inteins are protein-intervening sequences that can self-excise and concomitantly splice together the flanking polypeptides. Two-piece split inteins capable of protein trans-splicing have been found in nature and engineered in laboratories, but they all have a similar split site corresponding to the endonuclease domain of the intein. Can inteins be split at other sites and do transsplicing? After testing 13 split sites engineered into a Ssp DnaB mini-intein, we report the finding of three new split sites that each produced a two-piece split intein capable of protein trans-splicing. These three functional split sites are located in different loop regions between ␤-strands of the intein structure, and one of them is just 11 amino acids from the beginning of the intein. Because different inteins have similar structures and similar ␤-strands, these new split sites may be generalized to other inteins. We have also demonstrated for the first time that a three-piece split intein could function in protein trans-splicing. These findings have implications for intein structure-function, evolution, and uses in biotechnology.An intein is a protein-intervening sequence that catalyzes a protein-splicing reaction in which the intein sequence is precisely excised and its flanking sequences (N-and C-exteins) join with a peptide bond to produce the mature host protein (spliced protein) (1). The mechanism of protein splicing typically has four steps: two acyl rearrangements at the two splicing junctions, a trans-esterification between the two junctions, and a cyclization of the Asn residue at the C-terminal junction (2-4). Crystal structures of inteins revealed a splicing domain consisting of 11-12 ␤-strands and forming a compact horseshoe shape with the splicing junctions located in the central cleft (5-11). A majority of inteins also have a homing endonuclease domain inserted in the splicing domain sequence (12). These bifunctional inteins are ϳ350 -550 amino acids (aa) 1 long, although some extra large inteins are up to 1650 aa long and also contain tandem repeats (13,14). Nearly 200 intein and inteinlike sequences have been found in a wide variety of host proteins and in microorganisms belonging to bacteria, Archaea, and eukaryotes (12,15). Their sporadic phylogenetic distributions suggest lateral gene transfer through intein homing (16,17). Inteins generally share only low levels of sequence similarity, but they share striking similarities in structure, reaction mechanism, and evolution (4,18,19,21). It is thought that inteins first originated with just the splicing domain and then acquired the endonuclease domain, with the latter conferring genetic mobility to the intein. During intein evolution, however, some inteins lost their endonuclease domain to become mini-inteins consisting of just the ϳ130-aa protein-splicing domain plus a linker sequence of various lengths in place of the endonuclease domain (12,22).An interesting event of intein evolution is the loss of sequence continuity in some inteins, which apparently produced ...

The fucoidan from Ascophyllum nodosum attenuates atherosclerosis by up-regulating reverse cholesterol transport.

Intein-based protein cleavages, if carried out in a controllable way, can be useful tools of recombinant protein purification, ligation, and cyclization. However, existing methods using contiguous inteins were often complicated by spontaneous cleavages, which could severely reduce the yield of the desired protein product. Here we demonstrate a new method of controllable cleavages without any spontaneous cleavage, using an artificial S1 split-intein consisting of an 11-aa N-intein (I N ) and a 144-aa C-intein (I C ). In a C-cleavage design, the I C sequence was embedded in a recombinant precursor protein, and the small I N was used as a synthetic peptide to trigger a cleavage at the C-terminus of I C . In an N-cleavage design, the short I N sequence was embedded in a recombinant precursor protein, and the separately produced I C protein was used to catalyze a cleavage at the N-terminus of I N . These N-and C-cleavages showed >95% efficiency, and both successfully avoided any spontaneous cleavage during expression and purification of the precursor proteins. The N-cleavage design also revealed an unexpected and interesting structural flexibility of the I C protein. These findings significantly expand the effectiveness of intein-based protein cleavages, and they also reveal important insights of intein structural flexibility and fragment complementation.

lncRNA metastasis-associated lung adencarcinoma transcript 1 (MALAT1) plays an important role in the metastasis of lung cancer. Yet, its role in bone metastasis and the related mechanism remain unknown. The present study aimed to investigate the role of lncRNA MALAT1 in the bone metastasis of non-small cell lung cancer (NSCLC), including the expression pattern in tumor tissues, and the effect on the apoptosis, proliferation, migration and invasion of NSCLC cells. The expression level of MALAT1 in NSCLC tissues with/without bone metastasis and in NSCLC cell lines with (ACC-LC-319/bone2)/without (SPC‑A1) bone metastatic ability was determined with qRT-PCR and compared with t-test. si-MALAT1 was used to downregulate the expression of MALAT1 in ACC-LC-319/bone2 cells. The proliferation ability was assessed by MTT assay, and the apoptosis, migration, invasion and tumorigenesis in vivo were also assessed to detect the effect of MALAT1 expression on NSCLC cells. In conclusion, the present study found that MALAT1 was significantly highly expressed in NSCLC tissues with bone metastasis and in NSCLC cell lines with high bone metastatic ability (P<0.0001). Downregulation of MALAT1 expression significantly inhibited proliferation and induced cell apoptosis in comparing with the negative controls. Our results also revealed that MALAT1 significantly increased the migration, invasion and tumorigenesis in vivo, which suggests its important role in the bone metastasis of NSCLC.

Gut microbiota imbalance is found in fecal samples from DN patients, in which Roseburia intestinalis is significantly decreased, while Bacteroides stercoris is increased. There is a significant correlation between gut microbiota imbalance and clinical indexes related to lipid metabolism, glucose metabolism, and renal function. The gut microbiota may be predictive factors for the development and progression of DN, although further studies are warranted to illustrate their regulatory mechanisms.