Storage of monokaryotic strains of Podospora anserina

Maintenance of Podospora anserina strains for experimental purposes is very time consuming (see Esser 1969 Neurospora Newsl. 15:27-31) and methods have been published that address this issue by freezing ascospores at -80 oC (Begel and Belcour 1991 Fungal Genet. Newsl. 38:67). Although the latter approach does reduce the amount of time required for yearly sexual crosses and ascospore isolation, it does not resolve the problem of the time required to rapidly generate monokaryotic hyphae, that are needed as a source for inoculum for many types of experiments

Structural basis for the second step of group II intron splicing

The group II intron and the spliceosome share a common active site architecture and are thought to be evolutionarily related. Here we report the 3.7 Å crystal structure of a eukaryotic group II intron in the lariat-3′ exon form, immediately preceding the second step of splicing, analogous to the spliceosomal P complex. This structure reveals the location of the intact 3′ splice site within the catalytic core of the group II intron. The 3′-OH of the 5′ exon is positioned in close proximity to the 3′ splice site for nucleophilic attack and exon ligation. The active site undergoes conformational rearrangements with the catalytic triplex having dif- ferent configurations before and after the second step of splicing. We describe a complete model for the second step of group II intron splicing that incorporates a dynamic catalytic triplex being responsible for creating the binding pocket for 3′ splice site capture

Interrogating the Rights Discourse on Girls’ Education: Neo-Liberalism, Neo-Colonialism, and the Beijing Platform for Action

This article examines how girls’ education since 1995 has emerged as a prominent symbol within the ‘rights’ discourse coming out of the Beijing Platform for Action. By highlighting the neoliberal and neocolonial processes during this time, particular shifts are traced which show how girls’ education has been a symbolic part of the geopolitical canvas in Pakistan and Afghanistan alongside the ‘war on terror’ and universalisation of education. The article refers to alternative voices which have attempted to disrupt the global narrative of the post-Beijing ‘rights’ agenda and points to the problems of this in the context of occupations, militarisation, and markets being used simultaneously as strategies for global governance and order

Self-splicing of a group IIC intron: 5′ exon recognition and alternative 5′ splicing events implicate the stem–loop motif of a transcriptional terminator

Bacterial IIC introns are a newly recognized subclass of group II introns whose ribozyme properties have not been characterized in detail. IIC introns are typically located downstream of transcriptional terminator motifs (inverted repeat followed by T's) or other inverted repeats in bacterial genomes. Here we have characterized the self-splicing activity of a IIC intron, B.h.I1, from Bacillus halodurans. B.h.I1 self-splices in vitro through hydrolysis to produce linear intron, but interestingly, additional unexpected products were formed that were highly dependent on ionic conditions. These products were determined to represent alternative splicing events at the 5′ junction and cleavages throughout the RNA transcript. The alternative splicing and cleavage events occurred at cryptic splice sites containing stem–loop and IBS1 motifs, suggesting that the 5′ exon is recognized by both elements. These results provide the first example of a group II intron that uses 5′ splice sites nonadjacent to the ribozyme structure. Furthermore, the data suggest that IIC introns differ from IIA and IIB introns with respect to 5′ exon definition, and that the terminator stem–loop substitutes in part for the missing IBS2–EBS2 (intron and exon binding sites 2) interaction

The evolution of group II intron RNA structures and the characterization of a putatively primitive group IIC intron ribozyme

Bibliography: p. 167-178Some pages are in colour

Structure determination of group II introns

Group II introns are self-splicing catalytic RNAs that are able to excise themselves from pre-mRNAs using a mechanism identical to that utilized by the spliceosome. Both structural and phylogenetic data support the hypothesis that group II introns and the spliceosome share a common ancestor. Structures of group II introns have given insight into the active site required for the catalysis of RNA splicing. This review outlines crucial aspects of the structure determination of group II introns such as sample preparation and data processing. Given that group II introns are large RNAs that must be synthesized through in vitro transcription, there are special considerations that must be taken into account in terms of purification and crystallization, as compared to the isolation of large intact ribonucleoprotein complexes such as the ribosome. We specifically focus on the methodology used to determine the structure of the eukaryotic group II intron lariat from the brown algae Pylaiella littoralis. The techniques described in this review can also be applied for the structure determination of other large RNAs

Selecting New RNA Crystal Contacts

RNAs are relatively difficult to crystallize because many sequence variants must be tested to obtain suitable crystal contacts. In this issue of Structure, Shoffner et al. (2018) report an in crystallo selection procedure that allows for the rapid generation of new RNA crystal contacts

DOI: 10.1093/nar/gkg049 Database for mobile group II introns

Group II introns are self-splicing RNAs and retroelements found in bacteria and lower eukaryotic organelles. During the past several years, they have been uncovered in surprising numbers in bacteria due to the genome sequencing projects; however, most of the newly sequenced introns are not correctly identified. We have initiated an ongoing web site database for mobile group II introns in order to provide correct information on the introns, particularly in bacteria. Information in the web site includes: (1) introductory information on group II introns; (2) detailed information on subfamilies of intron RNA structures and intron-encoded proteins; (3) a listing of identified introns with correct boundaries, RNA secondary structures and other detailed information; and (4) phylogenetic and evolutionary information. The comparative data should facilitate study of the function, spread and evolution of group II introns. The database can be accessed a