Journal of Genetics and Genomics

Transcription-Coupled Replacement of Histones: Degradation or Recycling?

Yu-Shan Chen, Xiao-Bo Qiu

2012, 39(11): 575-580. doi: 10.1016/j.jgg.2012.09.001

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Abstract:
Histone modifications are proposed to constitute a “histone code” for epigenetic regulation of gene expression. However, recent studies demonstrate that histones have to be disassembled from chromatin during transcription. Recent evidence, though not conclusive, suggests that histones might be degradable after being removed from chromatin during transcription. Degradation of overexpressed excessive histones, instead of native histones, has been shown to be dependent on proteasomes and ubiquitination. Since the 26S proteasome usually recognizes polyubiquitinated substrates, it is critical to demonstrate whether degradation of histones is mediated by polyubiquitination. Unexpectedly, there is almost no evidence that any ubiquitin ligase can promote polyubiquitination-dependent degradation of constitutive histones. Meanwhile, acetylation and phosphorylation are also associated with histone degradation. This review attempts to summarize the current knowledge on the transcription-coupled degradation of histones and its regulation by posttranslational protein modifications.

Twin-Based DNA Methylation Analysis Takes the Center Stage of Studies of Human Complex Diseases

Dongfeng Zhang, Shuxia Li, Qihua Tan, Zengchang Pang

2012, 39(11): 581-586. doi: 10.1016/j.jgg.2012.07.012

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Abstract:
The etiology of complex diseases is characterized by the interaction between the genome and environmental conditions and the interface of epigenetics may be a central mechanism. Current technologies already allow us high-throughput profiling of epigenetic patterns at genome level. However, our understanding of the epigenetic processes remains limited. Twins are special samples in genetic studies due to their genetic similarity and rearing-environment sharing. In the past decades, twins have made a great contribution in dissecting the genetic and environmental contributions to human diseases and complex traits. In the era of functional genomics, the valuable samples of twins are helping to bridge the gap between gene activity and environmental conditions through epigenetic mechanisms unlimited to DNA sequence variations. We review the recent progresses in using twins to study disease-related molecular epigenetic phenotypes and link them with environmental exposures especially early life events. Various study designs and application issues will be highlighted and discussed with aim at making uses of twins in assessing the environmental impact on epigenetic changes during the development of complex diseases.

Distribution, Frequency and Variation of Stripe Rust Resistance Loci Yr10, Lr34/Yr18 and Yr36 in Chinese Wheat Cultivars

Cuiling Yuan, Hui Jiang, Honggang Wang, Kun Li, Heng Tang, Xianbin Li, Daolin Fu

2012, 39(11): 587-592. doi: 10.1016/j.jgg.2012.03.005

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Abstract:
Wheat stripe rust is a devastating disease in many regions of the world. In wheat, 49 resistance genes for stripe rust have been officially documented, but only three genes are cloned, including the race-specific resistance Yr10 candidate gene (Yr10) and slow-rusting genesLr34/Yr18 (hereafter designated as Yr18) and Yr36. In this study, we developed gene-specific markers for these genes and used them to screen a collection of 659 wheat accessions, including 485 Chinese cultivars. Thirteen percent and eleven percent of the tested Chinese cultivars were positive for the markers for Yr10 and Yr18 (the resistant haplotype of Yr18), respectively, but none were positive for the Yr36 marker. Since there is a limited use of the Yr10 gene in Chinese wheat, the relatively high frequency of wheat varieties with the Yr10 marker suggests that the identity of the Yr10 gene is unknown. With regards to the Yr18 gene, 29% of the tested cultivars that are used in the Middle and Lower Yangtze Valleys' winter wheat zone were positive for Yr18 markers. A non-functional allele of Yr18 was identified in ‘Mingxian 169’, a commonly used susceptible check for studying stripe rust. The data presented here will provide useful information for marker-assisted selection for wheat stripe rust resistance.

Amplification of an MFS Transporter Encoding Gene penT Significantly Stimulates Penicillin Production and Enhances the Sensitivity of Penicillium chrysogenum to Phenylacetic Acid

Jing Yang, Xinxin Xu, Gang Liu

2012, 39(11): 593-602. doi: 10.1016/j.jgg.2012.08.004

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Abstract:
Penicillin is historically important as the first discovered drug against bacterial infections in human. Although the penicillin biosynthetic pathway and regulatory mechanism have been well studied in Penicillium chrysogenum, the compartmentation and molecular transport of penicillin or its precursors are still poorly understood. In search of the genomic database, more than 830 open reading frames (ORFs) were found to encode transmembrane proteins of P. chrysogenum. In order to investigate their roles on penicillin production, one of them (penT) was selected and cloned. The deduced protein of penT belongs to the major facilitator superfamily (MFS) and contains 12 transmembrane spanning domains (TMS). During fermentation, the transcription of penT was greatly induced by penicillin precursors phenylacetic acid (PAA) and phenoxyacetic acid (POA). Knock-down of penT resulted in significant decrease of penicillin production, while over-expression of penT under the promoter of trpC enhanced the penicillin production. Introduction of an additional penT in the wild-type strain of P. chrysogenum doubled the penicillin production and enhanced the sensitivity ofP. chrysogenum to the penicillin precursors PAA or POA. These results indicate that penT stimulates penicillin production probably through enhancing the translocation of penicillin precursors across fungal cellular membrane.

Derivation of Germline Competent Rat Embryonic Stem Cells from DA Rats

Tianda Li, Xiao-Yang Zhao, Fei Teng, Xin Li, Minggui Jiang, Wei Li, Xuepeng Wang, Jialiang Wang, Lei Liu, Zhonghua Liu, Liu Wang, Qi Zhou

2012, 39(11): 603-606. doi: 10.1016/j.jgg.2012.06.006

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Abstract:

A Prototypic Jun Like Gene in Amphioxus Branchiostoma japonicum Expressed in Female Gonad

Qianghua Xu, Jun Tan, Liangbiao Chen

2012, 39(11): 607-611. doi: 10.1016/j.jgg.2012.05.011

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2012 Vol. 39, No. 11