Identification and characterization of two forms of mouse MUTYH proteins encoded by alternatively spliced transcripts

There are three types of mouse Mutyh mRNAs (type a, b and c) generated by alternative splicing, and type b mRNA is a major form among the three in most of the tissues examined. The level of type c mRNA is relatively high in brain. Type a and b mRNAs were expected to encode 57.7 kDa protein (MUTYHalpha), while type c mRNA had a partly different open reading frame encoding a 50.2 kDa protein (MUTYHbeta). An in vitro translation of type b and c mRNAs produced a 50 kDa MUTYHalpha and 47 kDa MUTYHbeta, respectively. MUTYHalpha and MUTYHbeta were detected in wild-type embryonic stem (ES) cells or thymocytes prepared from wild-type mice, but neither MUTYH-null ES cells nor thymocytes prepared from MUTYH-null mice. Both MUTYHalpha and MUTYHbeta were mainly localized in the nuclei and some in mitochondria in wild-type ES cells. Recombinant MUTYHalpha and beta were expressed as fusion proteins with thioredoxin in Escherichia coli, but only MUTYHalpha was partly soluble and thus could be purified. Recombinant MUTYHalpha possessed DNA glycosylase activities to excise adenine opposite 8-oxoguanine and guanine but not AP lyase activity.     

Cloning and expression of an ABSCISIC ACID-INSENSITIVE 3 (ABI3) gene homologue of yellow-cedar (Chamaecyparis nootkatensis)

A homologue of the ABI3 gene was isolated from the conifer species, Chamaecyparis nootkatensis. The deduced protein of 794 amino acids exhibited sequence similarity to other VP1/ABI3 proteins within four regions. Expression occurs exclusively in seeds, with no detectable mRNA in leaves and roots. Unlike the homologues of angiosperms, CnABI3 may be encoded by more than one gene.     

The ABSCISIC ACID-INSENSITIVE 3 (ABI3) gene is expressed during vegetative quiescence processes in Arabidopsis

The ABSCISIC ACID-INSENSITIVE 3 ( ABI3 ) gene of Arabidopsis thaliana (L.) Heynh is known to play an important role during seed maturation and dormancy. Here, we present evidence suggesting an additional role for ABI3 during vegetative quiescence processes. During growth in the dark, ABI3 is expressed in the apex of the seedlings after cell division is arrested. The 2S seed storage protein gene, a target gene of ABI3 in seeds, is also induced in the arrested apex under similar darkness conditions. In addition, β -glucuronidase expression under the control of the ABI3 promoter is abolished by treatments that provoke leaf development in the dark [sucrose and abscisic acid (ABA) biosynthesis inhibitors] and induced by treatments that prevent leaf development (darkness and ABA). Furthermore, ABI3 expression is absent in apices of dark-grown de-etiolated ( det 1 ) and abi3 mutants, both known to develop leaves or leaf primordia in the dark. The fact that the expression of the ABI3 gene is only observed in a fraction of the analysed plants suggests that ABI3 is probably only one of the components of a molecular network underlying quiescence. In addition to the expression of ABI3 in apices of dark-grown seedlings, the ABI3 promoter confers expression in other vegetative organs as well, such as the stipules and the abscission zones of the siliques. In conclusion, apart from its role in seed development, ABI3 might have additional functions.     

The differential expression of alternatively spliced transcripts and imprinting status of MEG9 gene in cows

Meg9/Mirg (maternally expressed gene 9/microRNA containing gene), a non‐coding RNA (ncRNA) comprising many alternatively splicing isoforms, has been identified as maternally expressed in mouse and sheep, but its imprinting status and splicing variants are still unknown in cattle. In this study, we found three splicing variants of the cattle MEG9 gene expressed in a tissue‐specific manner. A single nucleotide polymorphism site (SNP c.1354C>G) was identified in exon 3 of cattle MEG9 and used to distinguish between monoallelic and biallelic expression. Our results showed that MEG9 exhibited monoallelic expression in all examined cattle tissues by comparing sequencing results between genomic DNA and cDNA levels at the c.1354C>G SNP site, suggesting that MEG9 is imprinted in cattle.