江西赣江源区域两栖动物的群落组成和物种多样性特征

赣江发源于武夷山脉南段西麓的高山岭间,该区域独特的地理环境和气候特征蕴育了丰富的生物多样性。然而关于该区域两栖动物群落组成和物种多样性调查非常匮乏,不利于赣江源头两栖动物物种多样性的保护。于2016年4-9月期间在江西赣江源区域采用样线法调查了两栖动物的资源状况、群落组成及物种多样性特征,比较了它们在山地森林区、丘陵森林与农田区和盆地农田区3类栖息地之间的差异性。结果表明：赣江源区域分布有8科23种两栖动物,新增记录3个物种,包括尖舌浮蛙、寒露林蛙和九龙棘蛙,泽陆蛙和饰纹姬蛙为优势种。赣江源区域的两栖动物群落组成和物种多样性存在显著的季节间差异和栖息地间差异;两栖动物季节性繁殖是造成前者差异的主要因素,而土地利用类型、栖息地特征、空间距离、生活习性的物种特性等因素成就了后者差异的出现。因此,春、夏季一般有比秋季见到更高的两栖动物物种丰富度和多样性;山地森林区的两栖动物物种丰富度和多样性最高,盆地农田区次之,丘陵森林与农田区的最低。山地森林区应成为赣江源区域两栖动物多样性保护的优先区域。国家Ⅱ级重点保护野生动物虎纹蛙,在3类栖息地中均有分布,且在盆地农田区和山地森林区能见到更多个体,但农田区分布的虎纹蛙遭受到更大的威胁,建议加强对农田区虎纹蛙及其栖息地的保护。     

中国两栖动物受威胁现状评估

为了了解我国两栖动物受威胁现状和致危因素,进而制定相关的保护措施和开展国际合作,本文依据中国两栖动物野生种群与生境现状,利用《IUCN物种红色名录濒危等级和标准》(3.1版)和《IUCN物种红色名录标准在国家或地区的应用指南》(4.0版),对中国已知的408种两栖动物的濒危状况进行了评估,并编制了《中国两栖动物红色名录》。评估结果表明:中国两栖动物有1种灭绝,1种区域灭绝,受威胁的两栖动物共计176种,占评估物种总数的43.1%,明显高于《IUCN濒危物种红色名录》(2015)的物种受威胁率(30.8%)。中国两栖动物特有种272种,其中48.9%属于受威胁物种。中国两栖动物受威胁比例最高的目是有尾目(63.4%),明显高于无尾目(39.0%);受威胁比例最高的科是隐鳃鲵科(Cryptobranchidae)(仅有1种,100%受威胁),小鲵科(Hynobiidae)(86.7%)和叉舌蛙科(Dicroglossidae)(78.1%)。有11个省区的受威胁物种数占本省区两栖动物物种总数的30%及以上,前3位分别是四川(40.8%)、广西(39.2%)和云南(37%)。中国大多数两栖动物物种分布在西南山地和华南地区,以海拔2,000 m以下区域为主。栖息地退化或丧失、捕捉、环境污染列受威胁两栖动物致危因子的前3位。鉴于中国两栖动物区系的复杂性和独特性,进一步加强两栖动物资源调查、种群和生境监测及相关科学研究,仍是今后一段时期开展两栖动物多样性保护和濒危物种拯救行动的关键性基础工作。     

江西桃红岭梅花鹿国家级自然保护区两栖动物资源调查

江西桃红岭梅花鹿国家级自然保护区自成立以来,一直未进行过两栖动物资源调查。为掌握两栖动物本底资源现状,评价当地的生物多样性,作者于2005年4月下旬至5月上旬、8月中旬、2006年7月下旬,前后3次对该保护区两栖动物资源进行了实地调查。保护区现已记录两栖动物19种,隶属2目7科,占江西省39种两栖动物的48.72%。其中以16种东洋界物种为主,广布种3种,无古北界物种。东洋界物种包括10种华中区与华南区共有种及6种华中区物种。这种动物区系组成特点与保护区在动物地理区划上属东洋界华中区东部丘陵平原亚区一致。此次考察增加赣北(鄱阳湖)平原省两栖动物新纪录6种,分别是中国雨蛙(Hyla chinensis)、弹琴蛙(Hylarana adenopleura)、阔褶水蛙(H.latouchii)、花臭蛙(Odorrana schmackeri)、斑腿树蛙(Rhacophorus megacephalus)和小弧斑姬蛙(Microhyla heymonsi)。最后,结合调查结果对保护区内两栖动物的分布和资源现状进行了分析。     

福建省两栖、爬行动物更新名录

区域物种编目及适时更新是生物多样性研究和保护实践的必要前提。本文基于福建省全省网格化的野外调查, 并整合文献资料(截至2021年12月), 更新了该省现生本土两栖、爬行动物名录。本名录共收录两栖动物2目9科29属55种、爬行动物2目25科72属126种。其中, 分别有4种两栖动物和2种爬行动物是福建省特有种; 24种两栖动物和18种爬行动物的模式产地位于福建省。与《福建省两栖动物区系及地理区划》和《福建省爬行动物区系及地理区划》的物种名录相比, 本名录新增物种22种, 删除8个物种, 修订64个物种的名称。有6种爬行动物被列为国家I级重点保护动物, 分别有5种两栖动物和25种爬行动物被列为II级保护动物。10种两栖动物被《中国生物多样性红色名录•脊椎动物(第四卷): 两栖动物》评估为受胁物种(2种极危, 1种濒危, 7种易危, 分别占两栖动物物种数的3.64%、1.82%和12.73%); 41种爬行动物被《中国生物多样性红色名录•脊椎动物(第三卷): 爬行动物》评估为受胁物种(11种极危, 15种濒危, 15种易危, 分别占物种数的8.73%、11.90%和11.90%)。     

麻阳河国家级自然保护区两栖爬行动物资源调查

为进一步了解麻阳河国家级自然保护区两栖爬行类的资源分布和物种多样性特征,于2013年5~6月对麻阳河国家级自然保护区两栖爬行动物资源进行了实地考察。调查结果显示,麻阳河国家级自然保护区有两栖爬行动物43种,隶属4目14科34属。运用相似性指数对麻阳河、佛顶山、雷公山三个自然保护区两栖爬行动物进行比较,印证了动物地理区划上雷公山和佛顶山属于黔东南低山丘陵盆地省,麻阳河属于黔北中山峡谷省的划分。运用G-F指数公式分别计算三个自然保护区两栖动物和爬行动物G-F指数,其中,雷公山两栖动物和爬行动物G-F指数最高,分别为0.23和0.50,麻阳河两栖动物和爬行动物G-F指数最低,分别为﹣0.20和0.25,说明麻阳河国家级自然保护区中两栖动物和爬行动物的科间和科内多样性均较低。通过对三个自然保护区年均降水量、年均温等环境因子分析比较,得出麻阳河国家级自然保护区两栖爬行动物物种相对较少的原因,可能是麻阳河国家级自然保护区较低的年均降水量和较高的年均温。     

黑石顶自然保护区两栖动物资源和区系特征的研究

报道了黑石顶自然保护区两栖动物资源和区系特征的调查结果．已知有２１种（包括亚种）１１属７科２目．在２１种两栖动物中,它们都属于东洋界物种,其中华中区和华南区的共有物种占６１．８％,而属华中区的物种占１９．１％属华南区的物种也占１９．１％．还分析了黑石顶自然保护区两栖动物群落的水平分布和垂直分布的特征     

贵州两栖动物区系及地理区划的初步研究

本文报道贵州省两栖动物63种,其中省新纪录2种,即阔褶蛙和锯腿树蛙。将贵州划分为黔西高原中山、黔北中山峡谷、黔中山原丘陵、黔东南低山丘陵盆地和黔南低山河谷五个动物地理省。认为黔南低山河谷省属于向华南区过渡的华中地带。讨论了各动物地理省的地貌、气候、两栖动物区系特征及地理替代种类。分析了各动物地理省两栖动物区系的相似性及数量关系。     

西南喀斯特地貌区两栖动物丰富度分布格局与环境因子的关系

物种丰富度分布格局的成因机制一直是宏观生态学研究的热点问题之一。中国西南地区喀斯特地貌区(以广西、云南和贵州为主)是世界上面积最大的喀斯特地貌区,也是全球范围内34个生物多样性热点地区之一。为了解该区域两栖动物物种丰富度分布格局及其与环境因子之间的关系,本研究根据中国科学院成都生物研究所标本馆、中国科学院昆明动物研究所标本馆、广西壮族自治区自然博物馆和中南林业科技大学动物标本室收藏的标本数据,以及公开发表的文献数据,共获得18,246条两栖动物记录(219个物种),然后运用生态位模型估测每个物种的潜在分布区,并把每个物种的潜在分布区叠加起来,最终得到该区域在10km×10km生态位模型空间尺度上的两栖物种丰富度地理分布格局图,最后进行多元回归和模型选择分析。结果表明:有12种两栖动物仅在喀斯特地貌区分布,占物种总数的5.48%;有104种两栖动物仅在非喀斯特地貌区分布,占物种总数的47.49%;有103种两栖动物在喀斯特地貌区和非喀斯特地貌区均有分布,占物种总数的47.03%;两栖动物物种丰富度随纬度的增高而降低;地貌类型(喀斯特地貌和非喀斯特地貌)对两栖动物物种丰富度的分布格局有显著影响(χ~2=36.47, P 0.0001),但模型拟合效果差(McFadden’s Rho square=0.0037)。影响该区域两栖动物物种丰富度分布格局最大的环境因子是年均降雨量(R~2=0.232, P 0.001),其次是最干月平均降雨量(R~2=0.221, P 0.001)。该区域两栖动物物种丰富度的格局主要是由地貌和不同的环境因子共同相互作用的结果,不过仍有相当一部分物种丰富度的分布格局未被解释。因此,要更全面地认识该区域两栖动物物种丰富度格局的形成机制,有必要加强干扰、捕食、竞争等其他生物因子的影响研究。     

福建省两栖类物种多样性评估

地区性物种多样性评价是当前全球生物多样性研究的重要组成部分。本文采用G-F指数对福建省两栖类物种多样性进行评估,同时利用弦距离类间平均连锁的方法对福建省22个县（市）和5个两栖动物地理省进行聚类分析。结果表时：福建省各县（市）的两栖类物种多样性差异较大,其中武夷山市两栖类物种多样性的G指数,F指数和G-F指数分别为2.978,4.863和0.388。处于华中区的3个地理省（闽北、闽东和闽西地理省）首先聚类,而后与处于华南区的闽中地理省聚类,最后与闽南地理省合并。聚类结果与福建省两栖动物地理区划大体一致,但个别县（市）不太相符,作者建议将大田县划归在华中区的闽西地理省。     

海南岛稻田两栖动物资源调查及保护对策探讨

2006年5月～2008年2月对海南岛稻田两栖动物资源进行了野外调查,共采得两栖动物标本15种,隶属于5科11属,结合文献资料,海南岛有两栖动物38种,隶属7科20属.其区系组成东洋界种类明显占优势,占总物种的93.33%,特有种占13.3%.     

Lactones of disialyl lactose: characterisation by NMR and mass spectra

The lactonisation of alpha-Neup5Ac-(2-->8)-alpha-Neup5Ac-(2-->3)-beta-D-Galp-(1-->4)-D-Glc (disialyl lactose) was investigated. (1)H and (13)C NMR chemical shifts of disialyl lactose and alpha-Neup5Ac-(2-->8, 1-->9)-alpha-Neup5Ac-(2-->3, 1-->2)-beta-D-Galp-(1-->4)-D-Glc (disialyl lactose-dilactone) were assigned based on 1D and 2D NMR results, including edited HSQC, HSQC-TOSCY and HMBC. The time course of lactonisation was followed by thin layer chromatography (TLC) and high-performance liquid chromatography (HPLC) with electrospray ionisation (ESI) mass spectrometry (MS) detection. The rate of lactonisation between alpha-(8)Neu5Ac and alpha-(3)Neu5Ac residues (lactonisation at the alpha-(2-->8) linkage) was faster than that of lactonisation between alpha-(3)Neu5Ac and Gal residues (lactonisation at the alpha-(2-->3) linkage). The mass spectra of disialyl lactose, its lactones, alpha-Neup5Ac-(2-->8)-alpha-Neup5Ac (alpha-(2-->8) disialic acid) and alpha-Neup5Ac-(2-->3)-beta-D-Galp-(1-->4)-D-Glc-lactone (3'-sialyllactose-lactone) showed that the alpha-(2-->8) linkage between Neu5Ac residues is difficult to cleave in the ESI-MS, compared with the alpha-(2-->3) linkage between Neu5Ac and Gal residues.     

Depleting deubiquitinating enzymes promotes apoptosis in glioma cell line via RNA binding proteins SF2/ASF1

USP5 and USP8 (Deubiquitinating enzyme) are highly overexpressed and more recognized as poor prognosis marker in various cancers. Depleting USP5 or USP8 to assess the synergism with proteasome inhibitor (Bortezomib) were measured. Furthermore, in present finding USP5 cooperates hnRNPA1 & USP8 cooperate SF2/ASF1, therefore gain in expression of either hnRNPA1 or SF2/ASF1 is sufficient to promote cell survival. On the other side, apoptosis markers were more pronounced in U87 or T98G cells devoid of either USP5 or USP8. However, apparent increase in SF2/ASF1 in absence of USP5, providing resistant factor is new. Antiapoptotic activity due to rise in SF2/ASF1 was validated after co-knock down of SF2/ASF1 in addition to USP5 induces more apoptosis comparing to individual knock down of USP5 or SF2/ASF1. This reveals SF2/ASF1 (RNA binding protein) delayed the apoptotic effect due to loss of USP5, lends ubiquitination of hnRNPA1. In presence of USP5, PI3 kinase inhibition promotes even more interaction between USP5 and hnRNPA1, thereby stabilizes hnRNPA1 in U87MG. In that way hnRNPA1 and SF2/ASF1 impart oncogenic activity. In conclusion, siRNA based strategy against USP5 is not enough to inhibit glioma, moreover targeting additionally SF2/ASF1 by knocking down USP8 is suitably more effective to deal with glioma tumour reoccurrence by indirectly targeting both SF2/ASF1 and hnRNPA1 oncogene.     

Chemoenzymatic synthesis of 2-azidoethyl-ganglio-oligosaccharides GD3, GT3, GM2, GD2, GT2, GM1, and GD1a

We have synthesized several ganglio-oligosaccharide structures using glycosyltransferases from Campylobacter jejuni. The enzymes, alpha-(2-->3/8)-sialyltransferase (Cst-II), beta-(1-->4)-N-acetylgalactosaminyltransferase (CgtA), and beta-(1-->3)-galactosyltransferase (CgtB), were produced in large-scale fermentation from Escherichia coli and further characterized based on their acceptor specificities. 2-Azidoethyl-glycosides corresponding to the oligosaccharides of GD3 (alpha-D-Neup5Ac-(2-->8)-alpha-D-Neup5Ac-(2-->3)-beta-D-Galp-(1-->4)-beta-D-Glcp-), GT3 (alpha-D-Neup5Ac-(2-->8)-alpha-D-Neup5Ac-(2-->8)-alpha-D-Neup5Ac-(2-->3)-beta-D-Galp-(1-->4)-beta-D-Glcp-), GM2 (beta-D-GalpNAc-(1-->4)-[alpha-D-Neup5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-Glcp-), GD2 (beta-D-GalpNAc-(1-->4)-[alpha-D-Neup5Ac-(2-->8)-alpha-D-Neup5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-Glcp-), GT2 (beta-D-GalpNAc-(1-->4)-[alpha-D-Neup5Ac-(2-->8)-alpha-D-Neup5Ac-(2-->8)-alpha-D-Neup5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-Glcp-), and GM1 (beta-D-Galp-(1-->3)-beta-D-GalpNAc-(1-->4)-[alpha-D-Neup5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-Glcp-) were synthesized in high yields (gram-scale). In addition, a mammalian alpha-(2-->3)-sialyltransferase (ST3Gal I) was used to sialylate GM1 and generate GD1a (alpha-D-Neup5Ac-(2-->3)-beta-D-Galp-(1-->3)-beta-D-GalpNAc-(1-->4)-[alpha-D-Neup5Ac-(2-->3)]-beta-D-Galp-(1-->4)-beta-D-Glcp-) oligosaccharide. We also cloned and expressed a rat UDP-N-acetylglucosamine-4'epimerase (GalNAcE) in E. coli AD202 cells for cost saving in situ conversion of less expensive UDP-GlcNAc to UDP-GalNAc.     

Purine 8-substitution modulates the ribonuclease L binding and activation abilities of 2',5'-oligoadenylates

Analogues of the 2',5'-linked adenylate trimers monophosphate (p5'A2'p5'A2'p5'A) containing 8-hydroxypropyladenosine, 8-bromoadenosine, and 8-hydroxyadenosine in the first, second, and third nucleotide positions were tested for their ability to bind to and activate RNase L of mouse L cells. p5'AHPr2'p5'AHPr2'p5'AHPr (pAHPr3) (1b) and p5'ABr2'p5'ABr2'p5'ABr (pABr3) (1d) were markedly decreased in ability to bind to the 2-5A dependent endonuclease. On the other hand, analogue of the 2',5'-linked adenylate trimer monophosphate substituted by 8-hydroxyadenosine in the first, second, and third nucleotide position was bound about as well as parent 2-5A [pppA(2'p5'A)2] (p3A3) (1e) to RNase L. Additionally, p5'AOH2'p5'AOH2'p5'AOH (pAOH3) (1c) was as active as parent 2-5A in the rRNA cleavage assay, while pAHPr3 (1b) and pABr3 (1d) were devoid of activity. The 8-substituted analogues of 2-5A were more resistant to the degradation by the (2',5') phosphodiesterase. Finally of particular interest was monophosphate, pAOH3 (1c) which possessed nearly 100% of the translation inhibitory activity of 2-5A triphosphate itself. These results suggest that changes in the base-sugar torsion angles of 2-5A may modulate both binding to and activation of mouse L cell RNase L.     

Establishment of a quantitative bovine CXCL8 sandwich ELISA with newly developed monoclonal antibodies

Three IgG class anti-bovine CXCL8 (bCXCL8) monoclonal antibody (mAb)-secreting hybridomas, SH8-8D7, SH8-12A5 and SH8-2A1, were developed. SH8-8D7 was IgG2a, and SH8-12A5 and SH8-2A1 were IgG1. All three mAbs detected recombinant bCXCL8 (rbCXCL8) by immunoprecipitation and Western blotting. SH8-2A1 could neutralise the chemotactic activity of rbCXCL8 towards neutrophils. The quantitative bCXCL8 ELISA was constituted by the combination of SH8-12A5 and biotin-SH8-2A1. The detection range was 20-1000 pg/mL. A sandwich ELISA was used to measure native bCXCL8 derived from the supernatant of cultured bovine peripheral blood mononuclear cells stimulated with ConA, LPS or PHA. Furthermore, SH8-2A1 could detect bCXCL8 in formalin-fixed, paraffin-embedded, pneumonic calf tissues. These findings indicate that the newly developed anti-bCXCL8 mAbs could contribute to research on bovine inflammatory responses and immunology.     

The U5 snRNA internal loop 1 is a platform for Brr2, Snu114 and Prp8 protein binding during U5 snRNP assembly

The U5 small nuclear ribonucleoprotein particle (snRNP) forms the heart of the spliceosome which is required for intron removal from pre‐mRNA. The proteins Prp8, Snu114 and Brr2 all assemble with the U5 small nuclear RNA (snRNA) to produce the U5 snRNP. Successful assembly of the U5 snRNP, then incorporation of this snRNP into the U4/U6.U5 tri‐snRNP and the spliceosome, is essential for producing an active spliceosome. We have investigated the requirements for Prp8, Snu114 and Brr2 association with the U5 snRNA to form the U5 snRNP in yeast. Mutations were constructed in the highly conserved loop 1 and internal loop 1 (IL1) of the U5 snRNA and their function assessed in vivo. The influence of these U5 mutations on association of Prp8, Snu114 and Brr2 with the U5 snRNA were then determined. U5 snRNA loop 1 and both sides of IL1 in U5 were important for association of Prp8, Snu114 and Brr2 with the U5 snRNA. Mutations in the 3′ side of U5 IL1 resulted in the greatest reduction of Prp8, Snu114 and Brr2 association with the U5 snRNA. Genetic screening of brr2 and U5 snRNA mutants revealed synthetic lethal interactions between alleles in Brr2 and the 3′ side of U5 snRNA IL1 which reflects reduced association between Brr2 and U5 IL1. We propose that the U5 snRNA IL1 is a platform for protein binding and is required for Prp8, Brr2 and Snu114 association with the U5 snRNA to form the U5 snRNP. J. Cell. Biochem. 114: 2770–2784, 2013. © 2013 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals Inc.     

Biochemical evidence for ubiquitin ligase activity of the Arabidopsis COP1 interacting protein 8 (CIP8)

Arabidopsis COP1 is a negative regulator of photomorphogenesis, which targets HY5, a positive regulator of photomorphogenesis, for degradation via the proteasome pathway in the absence of light. COP1 and its interactive partner CIP8 both possess RING finger motifs, characteristic of some E3 ubiquitin ligases. Here we show that CIP8 promotes ubiquitin attachment to HY5 in E2-dependent fashion in vitro. CIP8 exhibits a strong interaction with the E2 enzyme AtUBC8 through its N-terminal domain. Phosphorylation of HY5 by casein kinase II requires the beta subunit 2, but does not affect HY5's susceptibility to ubiquitination. The RING domain of CIP8 is required but is not sufficient for ubiquitin ligase activity. Although the RING domain of CIP8 interacts with the RING domain of COP1, addition of recombinant COP1 fails to affect CIP8's ubiquitin ligase activity towards HY5 in vitro. However, recombinant COP1 can pull-down native CIP8 from the extract of dark-grown seedlings, but not from the extract of light-grown seedlings in a column-binding assay, implying a requirement for light-regulated modification in vivo. Our data suggest that CIP8 can form a minimal ubiquitin ligase in co-operation with the E2 enzyme AtUBC8. It is possible that the AtUBC8-CIP8 module might interact with COP1 in vivo, thereby participating in proteasome-mediated degradation of HY5.     

Sesquiterpene polyol esters from Tripterygium wilfordii

The extract (T(II)) of Tripterygium wilfordii Hook f. afforded four sesquiterpene esters: 1beta,2beta,5alpha,8beta,11-pentaacetoxy-4alpha-hydroxy-3alpha(2'-methylbutanoyl)-15-nicotinoyl-7-oxo-dihydroagarofuran; 1beta,5alpha,11-triacetoxy-7beta-benzoyl-4alpha-hydroxy-8beta-nicotinoyl-dihydroagarofuran; 1beta,2beta,5alpha,11-tetraacetoxy-8alpha-benzoyl-4alpha-hydroxy-7beta-nicotinoyl-dihydroagarofuran; 5alpha-benzoyl-4alpha-hydroxy-1beta,8alpha-dinicotinoyl-dihydro- agarofuran as well as one other known sesquiterpene ester. Their structures were established on the basis of spectroscopic studies.     

5-hydroxytryptamine4 receptor agonists facilitate cholinergic transmission in the circular muscle of guinea pig ileum: antagonism by tropisetron and DAU 6285.

The effect of 5-hydroxytryptamine (5-HT), BIMU 8 (endo-N-(8-methyl-8-azabicyclo [3.2.1.] oct-3-yl)-2,3-dihydro-3-(1-methyl)ethyl-2-oxo-1H-benzimidazole-1- carboxamide hydrochloride) and cisapride was studied on the electrically-induced neurogenic cholinergic twitch contractions in the guinea pig ileum circular muscle. These compounds caused a concentration-dependent increase in the amplitude of submaximal twitch contractions with the following rank order of potency: 5-HT greater than BIMU 8 = cisapride. The effect of 5-HT was competitively antagonized by tropisetron (ICS 205-930) (apparent pA2 value: 6.4), suggesting an interaction at 5-hydroxytryptamine4 (5-HT4) receptors. The novel benzimidazolone derivative DAU 6285 (endo-6-methoxy-8-methyl-8-azabicyclo [3.2.1.] oct-3-yl-2,3-dihydro-2-oxo-1H-benzimidazole-1-carboxylate hydrochloride), antagonized the effect of 5-HT, BIMU 8 and cisapride with apparent pA2 values in the range 7.1-7.3. Our findings demonstrate that cholinergic neurones innervating the circular coat are endowed with excitatory 5-HT4 receptors. DAU 6285 is approximately 5-9-fold more potent than tropisetron as antagonist at these receptors.     

Determinants of Nam8-dependent splicing of meiotic pre-mRNAs

Nam8, a component of yeast U1 snRNP, is optional for mitotic growth but required during meiosis, because Nam8 collaborates with Mer1 to promote splicing of essential meiotic mRNAs AMA1, MER2 and MER3. Here, we identify SPO22 and PCH2 as novel targets of Nam8-dependent meiotic splicing. Whereas SPO22 splicing is co-dependent on Mer1, PCH2 is not. The SPO22 intron has a non-consensus 5' splice site (5'SS) that dictates its Nam8/Mer1-dependence. SPO22 splicing relies on Mer1 recognition, via its KH domain, of an intronic enhancer 5'-AYACCCUY. Mutagenesis of KH and the enhancer highlights Arg214 and Gln243 and the CCC triplet as essential for Mer1 activity. The Nam8-dependent PCH2 pre-mRNA has a consensus 5'SS and lacks a Mer1 enhancer. For PCH2, a long 5' exon and a non-consensus intron branchpoint dictate Nam8-dependence. Our results implicate Nam8 in two distinct meiotic splicing regulons. Nam8 is composed of three RRM domains, flanked by N-terminal leader and C-terminal tail segments. The leader, tail and RRM1 are dispensable for splicing meiotic targets and unnecessary for vegetative Nam8 function in multiple synthetic lethal genetic backgrounds. Nam8 activity is enfeebled by alanine mutations in the putative RNA binding sites of the RRM2 and RRM3 domains.