Ribosomal 5S RNA (5S rRNA) is an integral component of the large ribosomal subunit in all known organisms with the exception only of mitochondrial ribosomes of fungi and animals. It is thought to enhance protein synthesis by stabilization of a ribosome structure. This paper presents the updated database of 5S rRNA and their genes (5S rDNA). Its short characteristics are presented in the Introduction. The database contains 2280 primary structures of 5S rRNA and 5S rRNA genes. These include 536 eubacterial, 61 archaebacterial, 1611 eukaryotic and 72 organelle sequences. The database is available on line through the World Wide Web at http://biobases.ibch.poznan.pl/5SData/.

The hypothetical replicase or replicase subunit cistron in the 5′‐proximal part of tobacco mosaic virus (TMV) RNA yields a major 126‐K protein and a minor 183‐K ‘readthrough’ protein in vivo and in vitro. Two natural suppressor tRNAs were purified from uninfected tobacco plants on the basis of their ability to promote readthrough over the corresponding UAG termination codon in vitro. In a reticulocyte lysate the yield of 183‐K readthrough protein increases from ˜10% in the absence of added tobacco plant tRNA up to ˜35% in the case of pure tRNATyr added. Their amino acid acceptance and anticodon sequence (GψA) identifies the two natural suppressor tRNAs as the two normal major cytoplasmic tyrosine‐specific tRNAs. tRNATyr1 has an A:U pair at the base of the TψC stem and an unmodified G10, whereas tRNATyr2 contains a G:C pair in the corresponding location and m2G in position 10. This is the first case that, in a higher eukaryote, the complete structure is known of both the natural suppressor tRNAs and the corresponding viral RNA on which they exert their function. The corresponding codon‐anticodon interaction, which is not in accordance with the wobble hypothesis, and the possible biological significance of the readthrough phenomenon is discussed.

5 S rRNA is an integral component of the large ribosomal subunit in all known organisms. Despite many years of intensive study, the function of 5 S rRNA in the ribosome remains unknown. Advances in the analysis of ribosome structure that have revealed the crystal structures of large ribosomal subunits and of the complete ribosome from various organisms put the results of studies on 5 S rRNA in a new perspective. This paper summarizes recently published data on the structure and function of 5 S rRNA and its interactions in complexes with proteins, within and outside the ribosome.

The non-coding RNAs database (http://biobases.ibch.poznan.pl/ncRNA/) contains currently available data on RNAs, which do not have long open reading frames and act as riboregulators. Non-coding RNAs are involved in the specific recognition of cellular nucleic acid targets through complementary base pairing to control cell growth and differentiation. Some of them are connected with several well known developmental and neuro-behavioral disorders. We have divided them into four groups. This paper is a short introduction to the database and presents its latest, updated edition.

Translation of tobacco mosaic virus (TMV) RNA in tobacco protoplasts yields the 17.5‐K coat protein, a 126‐K protein and a 183‐K protein which is generated by an efficient readthrough over the UAG termination codon at the end of the 126‐K cistron. In wheat germ extracts, however, only the 5′‐proximal 126‐K cistron is translated whereas the 183‐K readthrough protein is not synthesized. Purification and sequence analysis of the endogenous tyrosine tRNAs revealed that the uninfected tobacco plant contains two tRNAsTyr, both with GΨA anticodons which stimulate the UAG readthrough in vitro and presumably in vivo. In contrast, ˜85% of the tRNATyr from wheat germ contains a QΨA anticodon and ˜15% has a GΨA anticodon. Otherwise the sequences of tRNAsTyr from wheat germ and tobacco are identical. UAG readthrough and hence synthesis of the 183‐K protein is only stimulated by tRNATyrGΨA and not at all by tRNATyrQΨA. The tRNAsTyr from wheat leaves were also sequenced. This revealed that adult wheat contains tRNATyrGΨA only. This is very much in contrast to the situation in animals, where Q‐containing tRNAs are characteristic for adult tissues whereas Q deficiency is typical for the neoplastic and embryonic state.

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This paper presents the updated version (Y2K) of the database of ribosomal 5S ribonucleic acids (5S rRNA) and their genes (5S rDNA), http://rose.man/poznan.pl/5SData/index.html. This edition of the database contains 1985primary structures of 5S rRNA and 5S rDNA. They include 60 archaebacterial, 470 eubacterial, 63 plastid, nine mitochondrial and 1383 eukaryotic sequences. The nucleotide sequences of the 5S rRNAs or 5S rDNAs are divided according to the taxonomic position of the source organisms.

The effects of storage and deep desiccation on structural changes of DNA in orthodox seeds are poorly characterized. In this study we analyzed the 5-methylcytosine (m5C) global content of DNA isolated from seeds of common pear (Pyrus communis L.) that had been subjected to extreme desiccation, and the seedlings derived from these seeds. Germination and seedling emergence tests were applied to determine seed viability after their desiccation. In parallel, analysis of the global content of m5C in dried seeds and DNA of seedlings obtained from such seeds was performed with a 2D TLC method. Desiccation of fresh seeds to 5.3% moisture content (mc) resulted in a slight reduction of DNA methylation, whereas severe desiccation down to 2–3% mc increased DNA methylation. Strong desiccation of seeds resulted in the subsequent generation of seedlings of shorter height. A 1-year period of seed storage induced a significant increase in the level of DNA methylation in seeds. It is possible that alterations in the m5C content of DNA in strongly desiccated pear seeds reflect a reaction of desiccation-tolerant (orthodox) seeds to severe desiccation. Epigenetic changes were observed not only in severely desiccated seeds but also in 3-month old seedlings obtained from these seeds. With regard to seed storage practices, epigenetic assessment could be used by gene banks for early detection of structural changes in the DNA of stored seeds.