Holliday junction resolution by At-HIGLE: an SLX1 lineage endonuclease from Arabidopsis thaliana with a novel in-built regulatory mechanism.

Holliday junction is the key homologous recombination intermediate, resolved by structure-selective endonucleases (SSEs). SLX1 is the most promiscuous SSE of the GIY-YIG nuclease superfamily. In fungi and animals, SLX1 nuclease activity relies on a non-enzymatic partner, SLX4, but no SLX1-SLX4 like complex has ever been characterized in plants. Plants exhibit specialized DNA repair and recombination machinery. Based on sequence similarity with the GIY-YIG nuclease domain of SLX1 proteins from fungi and animals, At-HIGLE was identified to be a possible SLX1 like nuclease from plants. Here, we elucidated the crystal structure of the At-HIGLE nuclease domain from Arabidopsis thaliana, establishing it as a member of the SLX1-lineage of the GIY-YIG superfamily with structural changes in DNA interacting regions. We show that At-HIGLE can process branched-DNA molecules without an SLX4 like protein. Unlike fungal SLX1, At-HIGLE exists as a catalytically active homodimer capable of generating two coordinated nicks during HJ resolution. Truncating the extended C-terminal region of At-HIGLE increases its catalytic activity, changes the nicking pattern, and monomerizes At-HIGLE. Overall, we elucidated the first structure of a plant SLX1-lineage protein, showed its HJ resolving activity independent of any regulatory protein, and identified an in-built novel regulatory mechanism engaging its C-terminal region.

Effect of Vitamin D Supplementation on CD4 Count in HIV-Infected Children and Adolescents in North India: A Non-Randomized Comparative Study.

BACKGROUND: HIV infection is still a serious public health issue globally. Suboptimal vitamin D status is highly prevalent in HIV-infected children and adolescents throughout the world. OBJECTIVES: To evaluate the outcome of vitamin D supplementation on CD4 count in HIV-infected children and adolescents with suboptimal vitamin D status. METHODS: Vitamin D level of HIV-infected children and adolescents were measured at enrolment. Suboptimal vitamin D level was defined as 25(OH)D < 30 ng/ml. Vitamin D insufficiency and deficiency were defined as 21-29 and <20 ng/ml, respectively. Children with suboptimal vitamin D levels were supplemented with vitamin D. RESULTS: This was a single-centre, non-randomized comparative study enrolling 50 eligible participants. There were 20 patients who were vitamin D sufficient, 7 were vitamin D insufficient and 23 were found to be vitamin D deficient at enrolment. However, after supplementation, the status of sufficient remained same and 7 insufficient become sufficient, whereas in 23 deficient, 18 (78.3%) become sufficient and 5 (21.7%) become insufficient and this change was found statistically significant among the groups (χ2 = 6.52, p = 0.038). There was a significant improvement of CD4 count from baseline to 4 months in deficient group on vitamin D supplementation (p value < 0.001; 1.2-fold rise). No significant change was seen in vitamin D insufficient (p value = 0.791) and sufficient groups (p value = 0.168). CONCLUSION: Vitamin D should be supplemented in HIV-infected children on ART with low CD4 counts.

Giant Feeding Artery from Abdominal Aorta in Intralobar Pulmonary Sequestration.

Pulmonary sequestration (PS) is a rare congenital lung malformation. We present a case of newborn with antenatally diagnosed case of PS. The baby was delivered by cesarean section to primigravida mother at 38 + 3 weeks of gestation with birth weight of 2700 g. At 20 weeks of gestation, the antenatal ultrasound showed a triangular echogenic area in left lung supplied by feeding artery from descending aorta. The baby had respiratory distress soon after birth. Computerized tomographic pulmonary angiogram revealed abnormal blood supply of left lower lobe arising from descending aorta. The feeding vessel was abnormally large and was almost half of the diameter of the aorta. The baby underwent left lower lobectomy with double ligation of feeding artery at day 7 of life and was discharged on day 14 of life. Antenatal diagnosis of congenital lung malformation helps in careful planning of perinatal care and facilitates the early diagnosis and management.

Structural Aspects of DNA Repair and Recombination in Crop Improvement.

The adverse effects of global climate change combined with an exponentially increasing human population have put substantial constraints on agriculture, accelerating efforts towards ensuring food security for a sustainable future. Conventional plant breeding and modern technologies have led to the creation of plants with better traits and higher productivity. Most crop improvement approaches (conventional breeding, genome modification, and gene editing) primarily rely on DNA repair and recombination (DRR). Studying plant DRR can provide insights into designing new strategies or improvising the present techniques for crop improvement. Even though plants have evolved specialized DRR mechanisms compared to other eukaryotes, most of our insights about plant-DRRs remain rooted in studies conducted in animals. DRR mechanisms in plants include direct repair, nucleotide excision repair (NER), base excision repair (BER), mismatch repair (MMR), non-homologous end joining (NHEJ) and homologous recombination (HR). Although each DRR pathway acts on specific DNA damage, there is crosstalk between these. Considering the importance of DRR pathways as a tool in crop improvement, this review focuses on a general description of each DRR pathway, emphasizing on the structural aspects of key DRR proteins. The review highlights the gaps in our understanding and the importance of studying plant DRR in the context of crop improvement.