A novel ligation mediated-PCR based strategy for construction of subtraction libraries from limiting amounts of mRNA

Molecular cloning of growth hormone encoding cDNA of Indian major carps by a modified rapid amplification of cDNA ends strategy

A modified rapid amplification of cDNA ends (RACE) strategy has been developed for cloning highly conserved cDNA sequences. Using this modified method, the growth hormone (GH) encoding cDNA sequences of Labeo rohita, Cirrhina mrigala and Catla catla have been cloned, characterized and overexpressed in Escherichia coli. These sequences show 96-98% homology to each other and are about 85% homologous to that of common carp. Besides, an attempt has been made for the first time to describe a 3-D model of the fish GH protein.

RNA splicing of bacterial genes in eukaryotes

The presence of intervening sequences or introns in eukaryotic genes has been known for more than 20 years, and the mechanisms underlying RNA splicing have been studied in depth both genetically and biochemically. In recent years, however, an increasing number of bacterial genes have been introduced into higher eukaryotes as important tools for genetic studies. Their gene products are frequently used as an indirect measure for cell type-specific promoter activity, as, for example, in the case of chloramphenicol acetyl transferase (CAT assay) or beta-galactosidase. Here we show that RNA splicing of two prokaryotic genes encoding site-specific DNA recombinases occurs in eukaryotic cells. In one case, splicing is only observed after treatment of cells with the cytokine alpha interferon. We further demonstrate that mutating an intragenic donor splice site in a bacterial gene apparently activates a second, alternative splicing pathway. In conjunction with previous reports, our findings should also be regarded as a warning that splicing of bacterial genes in higher eukaryotes is a more common phenomenon than presently recognized, which may be difficult to overcome and may cause problems in the interpretation of experimental results.

Conjugation-specific genes in the ciliate Euplotes crassus: gene expression from the old macronucleus

Following mating or conjugation, the hypotrichous ciliate Euplotes crassus undergoes a massive genome reorganization process. While the nature of the rearrangement events has been well studied, little is known concerning proteins that carry out such processes. As a means of identifying such proteins, differential screening of a developmental cDNA library, as well as construction of a cDNA subtraction library, was used to isolate genes expressed only during sexual reproduction. Five different conjugation-specific genes have been identified that are maximally expressed early in conjugation, during the period of micronuclear meiosis, which is just prior to macronuclear development and the DNA rearrangement process. All five genes are retained in the mature macronucleus. Micronuclear, macronuclear, and cDNA clones of one gene (conZA7) have been sequenced, and the results indicate that the gene encodes a putative DNA binding protein. In addition, the presence of an internal eliminated sequence in the micronuclear copy of the conZA7 gene indicates that this conjugation-specific gene is transcribed from the old macronucleus.