tRFs and tRNA Halves: Novel Cellular Defenders in Multiple Biological Processes.

tRNA fragments derived from angiogenin or Dicer cleavage are referred to as tRNA-derived fragments (tRFs) and tRNA halves. tRFs and tRNA halves have been identified in both eukaryotes and prokaryotes and are precisely cleaved at specific sites on either precursor or mature tRNA transcripts rather than via random degradation. tRFs and tRNA halves are highly involved in regulating transcription and translation in a canonical or non-canonical manner in response to cellular stress. In this review, we summarize the biogenesis and types of tRFs and tRNA halves, clarify the biological functions and molecular mechanisms of tRNA fragments in both physiological and pathological processes with a particular focus on their cytoprotective roles in defending against oxidation and apoptosis, and highlight their potential application as biomarkers in determining cell fate.

Prolonging photoperiod promotes testosterone synthesis of Leydig cells by directly targeting local melatonin system in rooster testes†.

The study investigated the effects of prolonging photoperiod on the synthesis of testosterone and melatonin in roosters, and the effect of melatonin on testosterone synthesis in rooster Leydig cells as well as its molecular mechanisms. We randomly divided one hundred and twenty 20-week-old roosters into three groups and provided 6, 12.5 and 16 h light, respectively. The results showed that prolonging photoperiod promoted testosterone synthesis, decreased melatonin production, and inhibited the expression of melatonin membrane receptors MEL1A, MEL1B, MEL1C, and aralkylamine N-acetyltransferase (AANAT) in rooster testes. Subsequently, rooster Leydig cells were isolated and treated with 0, 0.1, 1, 10, and 100 ng/mL melatonin for 36 h. The results suggested that melatonin inhibited testosterone synthesis in rooster Leydig cells, and silencing MEL1A and MEL1B relieved the inhibition of melatonin on testosterone synthesis. Additionally, melatonin reduced the intracellular cyclic adenosine monophosphate (cAMP) level and the phosphorylation level of cAMP-response element binding protein (CREB), and CREB overexpression alleviated the inhibition of melatonin on testosterone synthesis. Furthermore, pretreatment with cAMP activator forskolin or protein kinase A (PKA) activator 8-bromo-cAMP blocked the inhibition of melatonin on CREB phosphorylation and testosterone synthesis. These results indicated that prolonging photoperiod promoted testosterone synthesis associated with the decrease in melatonin production and membrane receptors and biosynthetic enzyme of melatonin in rooster testes, and melatonin inhibited testosterone synthesis of rooster Leydig cells by inhibiting the cAMP/PKA/CREB pathway via MEL1A and MEL1B. This may be evidence that prolonging photoperiod could promote testosterone synthesis through the inhibition of the local melatonin pathway in rooster testes.

Low-density lipoprotein receptor-related protein 1 regulates muscle fiber development in cooperation with related genes to affect meat quality.

Low-density lipoprotein receptor-related protein 1 (LRP1) is an important signal protein that is widely involved in physiological processes, such as lipid metabolism, cell movement, and disease processes. However, the relationship between LRP1 and meat quality remains unknown in chickens. The present study aimed to investigate the correlation between LRP1 and meat quality that builds on our preliminary research, as well as to reveal the underlying molecular mechanism of LRP1 on meat-quality traits. The results showed that LRP1 was significantly correlated with shear force (P < 0.05). Several key genes involved in muscle growth and development, including IGF-1, IGFBP-5, IGF-1R, IGF-2, and MyoD, were down-regulated significantly (P < 0.05 or P < 0.01), and MSTN was up-regulated significantly (P < 0.01) in the presence of LRP1 interference. Cell proliferation- or apoptosis-related genes, including PMP22, CDKN2C, and p53, increased significantly (P < 0.05 or P < 0.01), whereas Bcl-x decreased significantly (P < 0.05) in the RNAi group. We conclude that LRP1 regulates muscle fiber development in cooperation with related genes that affect myoblast proliferation and apoptosis, thereby impacting shear force in chickens. This study will provide a valuable resource for biological investigations of muscle growth and meat-quality-related genes in chickens. The results could be useful in identifying candidate genes that could be used for selective breeding to improve meat quality.