Rational design of unrestricted pRN1 derivatives and their application in the construction of a dual plasmid vector system for Saccharolobus islandicus.

Saccharolobus islandicus REY15A represents one of the very few archaeal models with versatile genetic tools, which include efficient genome editing, gene silencing, and robust protein expression systems. However, plasmid vectors constructed for this crenarchaeon thus far are based solely on the pRN2 cryptic plasmid. Although this plasmid coexists with pRN1 in its original host, early attempts to test pRN1-based vectors consistently failed to yield any stable host-vector system for Sa. islandicus. We hypothesized that this failure could be due to the occurrence of CRISPR immunity against pRN1 in this archaeon. We identified a putative target sequence in orf904 encoding a putative replicase on pRN1 (target N1). Mutated targets (N1a, N1b, and N1c) were then designed and tested for their capability to escape the host CRISPR immunity by using a plasmid interference assay. The results revealed that the original target triggered CRISPR immunity in this archaeon, whereas all three mutated targets did not, indicating that all the designed target mutations evaded host immunity. These mutated targets were then incorporated into orf904 individually, yielding corresponding mutated pRN1 backbones with which shuttle plasmids were constructed (pN1aSD, pN1bSD, and pN1cSD). Sa. islandicus transformation revealed that pN1aSD and pN1bSD were functional shuttle vectors, but pN1cSD lost the capability for replication. These results indicate that the missense mutations in the conserved helicase domain in pN1c inactivated the replicase. We further showed that pRN1-based and pRN2-based vectors were stably maintained in the archaeal cells either alone or in combination, and this yielded a dual plasmid system for genetic study with this important archaeal model.

Enzymatic Switching Between Archaeal DNA Polymerases Facilitates Abasic Site Bypass.

Abasic sites are among the most abundant DNA lesions encountered by cells. Their replication requires actions of specialized DNA polymerases. Herein, two archaeal specialized DNA polymerases were examined for their capability to perform translesion DNA synthesis (TLS) on the lesion, including Sulfolobuss islandicus Dpo2 of B-family, and Dpo4 of Y-family. We found neither Dpo2 nor Dpo4 is efficient to complete abasic sites bypass alone, but their sequential actions promote lesion bypass. Enzyme kinetics studies further revealed that the Dpo4's activity is significantly inhibited at +1 to +3 site past the lesion, at which Dpo2 efficiently extends the primer termini. Furthermore, their activities are inhibited upon synthesis of 5-6 nt TLS patches. Once handed over to Dpo1, these substrates basically inactivate its exonuclease, enabling the transition from proofreading to polymerization of the replicase. Collectively, by functioning as an "extender" to catalyze further DNA synthesis past the lesion, Dpo2 bridges the activity gap between Dpo4 and Dpo1 in the archaeal TLS process, thus achieving more efficient lesion bypass.

Clinicopathological features and prognostic analysis of 77 patients with multiple primary cancers.

PURPOSE: The purpose of this study was to analyze the characteristics, diagnosis and treatment principles and prognosis of multiple primary cancers (MPC). METHODS: A total of 77 patients with MPC admitted in the Central Hospital of Changsha from December 2013 to December 2018 were enrolled in this retrospective analysis. The survival of these 77 patients with complete follow-up data was calculated. RESULTS: There were 77 patients with multiple primary cancers, including 70 patients with double primary cancers, 6 patients with three primary cancers, and 1 patient with four primary cancers. Among the 77 MPC patients, there were 4 synchronous carcinomas (SC), 58 metachronous carcinomas (MC), and 15 unknown cases. The 3, 5, and 10-year overall survival rates of 77 patients with follow-up data were 86.5%, 18.2%, and 12.9%, respectively. The median survival time of 4 SC and 58 MC patients was 12 months and 108 months, respectively. The median survival time was 48.5 months in 23 patients with an interval of less than 5 years, and 108 months in 29 patients with first and second primary cancers whose interval was more than 5 years. The median survival time of 26 patients with second primary lung cancer was 84 months, and that of 23 patients with second primary non-lung cancer was 156 months. CONCLUSIONS: MPCs are more likely to occur in the colorectum, and the prognosis of patients with metachronous cancer is better than that of patients with synchronous cancer. The longer the interval between two cancers, the better the prognosis will be. The prognosis of the second primary non-lung cancer patients is better than that of the lung cancer patients.

Biolistic Transformation of Haematococcus pluvialis With Constructs Based on the Flanking Sequences of Its Endogenous Alpha Tubulin Gene.

Haematococcus pluvialis has high commercial value, yet it displays low development of genetic transformation systems. In this research, the endogenous 5' and 3' flanking sequences of the constitutive alpha tubulin (tub) gene were cloned along with its encoding region in H. pluvialis, in which some putative promoter elements and polyadenylation signals were identified, respectively. Three selection markers of tub/aadA, tub/hyr and tub/ble with three different antibiotic-resistance genes fused between the endogenous tub promoter (Ptub) and terminator (Ttub) were constructed and utilized for biolistic transformation of H. pluvialis. Stable resistant colonies with introduced aadA genes were obtained after bombardments of either H. pluvialis NIES144 or SCCAP K0084 with the tub/aadA cassette, the efficiency of which could reach up to 3 × 10-5 per µg DNA through an established manipulation flow. Two key details, including the utilization of culture with motile flagellates dominant and controlled incubation of them on membrane filters during bombardments, were disclosed firstly. In obtained transformants, efficient integration and transcription of the foreign tub/aadA fragments could be identified through genome PCR examination and qPCR analysis, nonetheless with random style instead of homologous crossover in the H. pluvialis genome. The presented selection marker and optimized transforming procedures in this report would strengthen the platform for genetic manipulation and modification of H. pluvialis.

An oleaginous filamentous microalgae Tribonema minus exhibits high removing potential of industrial phenol contaminants.

Discharge of industrial phenol contaminants could cause great harm on natural environment. Through oleaginous microalgae cultivation in phenolic wastewater, pollutants can be phototrophically biofixed into biomass as feedstock for bioenergy production. It was firstly reported in this study that, an oleaginous filamentous microalgae Tribonema minus exhibited strong environmental phenol removal ability. T. minus filaments showed 449.46mgg-1 of phenol-uptake capacity, obviously higher than those strains with low phenol absorption such as Scenedesmus dimorphus. And phenols could be removed efficiently at the initial phenol concentration up to 700mgL-1. Simultaneously, through T. minus growth, phenol concentration could be decreased from 100mgL-1 to the range of 0.1-0.5mgL-1, which meet industrial discharge need of phenol contaminants in most countries. So Tribonema minus is a potential algal specie to help the construction of integrated process for both oleaginous biomass production and bioremediation of phenol contaminants.