Ultraviolet light-induced inhibition of small nuclear RNA synthesis

Differential alterations in metabolic pattern of the spliceosomal uridylic acid-rich small nuclear RNAs (UsnRNAs) during malignant transformation of 20-methylcholanthrene-induced mouse CNCI-PM-20 embryonic fibroblasts

Differential alterations of the spliceosomal Uridylic acid rich small nuclear RNAs (UsnRNAs) (U1, U2, U4, U5, and U6) are reported to be associated with cellular proliferation and development, but definitive information is scarce and also elusive. An attempt is made in this study to analyze the metabolic patterns of major spliceosomal UsnRNAs, during tumor development, in an in vitro carcinogenesis model of 20-methylcholanthrene (MCA)-transformed Swiss Mouse Embryonic Fibroblast (MEF), designated as CNCI-PM-20. MEF cells, after treatment with 20-MCA, progressed through a sequence of passages with distinct and heritable changes, finally becoming neoplastic at passage-42 (P42). A differential expression pattern of major UsnRNAs was observed during this process. The abundance of U1 was 20% below control (P1) at passage-20 (P20), followed by a gradual increase up until P42 (approximately 12% above the P1 value). The abundance of U2 was more or less constant during the cellular transformation. U4 showed a trend of increase, with above 30% abundance than control at P20, followed by a significant increase at P36 and P42 (1.5- and 2-fold, respectively, P-value <0.01). U5 also followed an identical pattern, with an increase of 70% compared to control (P-value <0.05) at P42. Interestingly, U6 gradually decreased from P20 onwards up until P42, with 22% at P20 and 67% at P42 (P-value <0.01). An overall significant quantitative alteration in abundance of U4, U5, and U6, observed in our study, contributes to the understanding of the fact that, the metabolism of major spliceosomal UsnRNAs is differentially regulated during the process of neoplastic transformation.

Self-propagating beta-sheet polypeptide structures as prebiotic informational molecular entities: the amyloid world

The idea is advanced that under the extreme earth conditions for ~3.9 billions years ago, protein-based beta-sheet molecular structures were the first self-propagating and information-processing biomolecules that evolved. The amyloid structure of these aggregates provided an effective protection against the harsh conditions known to decompose both polyribonucleotides and natively folded polypeptides. In the prebiotic amyloid world, both the replicative and informational functions were carried out by structurally stable beta-sheet protein aggregates in a prion-like mode involving templated self-propagation and storage of information in the beta-sheet conformation. In this amyloid (protein)-first, hybrid replication-metabolism view, the synthesis of RNA, and the evolvement of an RNA-protein world, were later, but necessary events for further biomolecular evolution to occur. I further argue that in our contemporary DNA<-->RNA-->protein world, the primordial beta-conformation-based information system is preserved in the form of a cytoplasmic epigenetic memory.

Did the first virus self-assemble from self-replicating prion proteins and RNA?

DNA is the molecule responsible for storing and processing genetic information today. In Earth's primeval environmental conditions, RNA was probably more suited for this function, due to its capability to act also as a catalytic enzyme. Some proteins are stable and reliable molecules even in extreme conditions, and under certain circumstances, proteins may play a role in transmitting certain phenotypes that are inherited in a non-Mendelian manner. When the dominant native state of a prion protein is replaced by a misfolded one, the resultant infective protein is associated with several neurological diseases in mammals. The misfolded proteins are remarkably resistant to even the most extreme environments. Prions are also associated with the transmission of certain fungal traits epigenetically, supporting the hypothesis that prions are a possible relic of an early stage of peptide evolution. The primitive world probably contained both self-replicating RNA molecules and prions, and prions attach easily to nucleic acids, and also fold and cause other proteins to fold in the same way. Consequently, a capsid could form from prion protein, enclosing the RNA, and perhaps creating the first RNA virus. A capsid originating from prion proteins would be a versatile and effective protection to RNA and could also explain some characteristics of virus self-assembly that are not well understood.

Epigallocatechin gallate induced apoptosis in Sarcoma180 cells in vivo: mediated by p53 pathway and inhibition in U1B, U4-U6 UsnRNAs expression

The aim of this study was to understand the mode of action of tea polyphenol epigallocatechin gallate (EGCG) in vivo. Swiss albino mice were treated i.p. with EGCG at two different doses i.e. 12-mg/kg body weight and 15-mg/kg body weight, for 7 days prior to inoculation of Sarcoma180 (S180) cells and continued for another 7 days. The growth of the S180, harvested 7 days after inoculation, was significantly reduced due to treatment with EGCG. The flowcytometric analysis of S180 cells, showed significant increase in apoptosis and reduction in the number of cells in G2/M phase of cell cycle due to treatment with EGCG. The induction of apoptosis has also been confirmed by the TUNEL and DNA fragmentation assays. Both RT-PCR and Western blot analysis showed significant up-regulation of p53 and bax, and down-regulation of bcl-2 and c-myc due to EGCG treatment. No changes in the expression pattern of p21, p27, bcl-xl, mdm2 and cyclin D1 were seen. Interestingly, there was significant down-regulation of spliceosomal uridylic acid rich small nuclear RNAs (UsnRNAs) U1B and U4-U6 due to EGCG treatment. This indicates that these UsnRNAs may be involved in the apoptosis process. Taken together, our study suggests that in vivo EGCG could induce apoptosis in S180 cells through alteration in G2/M phase of the cell cycle by up-regulation of p53, bax and down-regulation of c-myc, bcl-2 and U1B, U4-U6 UsnRNAs.

Differential Alterations in Metabolic Pattern of the Spliceosomal UsnRNAs during Pre-Malignant Lung Lesions Induced by Benzo(a)pyrene: Modulation by Tea Polyphenols

The differential alterations of the spliceosomal UsnRNAs (U1, U2, U4, U5, and U6) were reported to be associated with cellular proliferation and development. The attempt was made in this study to analyze the metabolic pattern of the spliceosomal UsnRNAs during the development of pre-malignant lung lesions induced in experimental mice model system by benzo(a)pyrene (BP) and also to see how tea polyphenols, epigallocatechin gallate (EGCG) and epicatechin gallate (ECG), modulate the metabolism of these UsnRNAs during the lung carcinogenesis. No significant changes in the level of the UsnRNAs were seen in the inflammatory lung lesions at 9th week due to treatment of BP. However, there was significant increase in the level of U1 ( approximately 2.5 fold) and U5 ( approximately 47%) in the hyperplastic lung lesions at 17th week. But in the mild dysplastic lung lesions at 26th week, the level of UsnRNAs did not change significantly. Whereas, in the dysplastic lung lesions at 36th week there was significant increase in the level of the U2 ( approximately 2 fold), U4 ( approximately 2.5 fold) and U5 ( approximately 2 fold). Due to the EGCG and ECG treatment the lung lesions at 9th week appeared normal and in the 17th, 26th, and 36th week it appeared as hyperplasia. The level of the UsnRNAs was significantly low in the lung lesions at 9th week (only U2 and U4 by EGCG), at 17th week (only U1 by EGCG/ECG), at 26th week (U1 by ECG; U2, U4 and U5 by EGCG/ECG) and at 36th week (U1 by ECG, U2 and U4 by EGCG/ECG). Whereas, there was significant increase in the level of U5 (by EGCG/ECG) and U6 (by EGCG only) in the lung lesions at 36th and 26th week respectively. This indicates that the metabolism of the spliceosomal UsnRNAs differentially altered during the development of pre-malignant lung lesions by BP as well as during the modulation of the lung lesions by the tea polyphenols.

Are prions related to the emergence of early life?

DNA and RNA are the modern cellular molecules related to the storage and processing of the genetic information. However, in the Earth primeval environment conditions, these two molecules are far from being the best option for this function due to their great complexity and sensibility to heat. Experiments have been showing that proteins are very stable and reliable molecules even in very extreme conditions and, under certain circumstances, could be related to the transmission of certain phenotypes that are inherited in a non-Mendelian manner. Prions, infective proteins that are associated to several neurological diseases among mammals by replacing their dominant native state of prion protein by a misfolded one, are remarkably resistant to even the most extreme environments. Furthermore, prions are also associated to the transmission of certain fungal traits in an epigenetical model. These two characteristics support the hypothesis that prions are a possible relic of early stage peptide evolution and may represent the reminiscence of a very ancient analogical code of biological transmission of information rather than the digital one represented by modern nucleic acids.

Differential alterations in metabolic pattern of the six major UsnRNAs during development

The uridylic acid rich nuclear RNAs (U1-U6 snRNAs) are involved mainly in the processing of pre-mRNA and pre-rRNA. So, any control of cell growth through pre-mRNA/pre-rRNA processing may have some regulation through altered UsnRNAs metabolism. With this idea, attempts have been made to see how the metabolism of the six major UsnRNAs' changed during the normal process of cellular proliferation associated with differentiation from pluripotent/totipotent stem cells of early embryonic stage to much more differentiated state of different cell/tissue lineages in different tissues/organs during the fetal and neonatal stages of growth. It has been seen that the levels of the six major UsnRNAs were high in day 8 embryo when the cells were mainly pluripotent/totipotent in nature, and during the progression of embryonic development the levels of these UsnRNAs gradually decreased (approximately 35-65%) up to the midgestational period (day 13) with some exception, when the organogenesis has already been started. However in the fetal life, the levels of these UsnRNAs were maximum or comparable around 18 +/- 2 days of gestation in comparison to that in day 8 embryo when the kinetics of the maturational status of the different organs were quite high. But, the levels of these UsnRNAs' became low during day 21 of fetal life or in day 0 of birth (perturation period) in all the tissues/organs except high UsnRNAs' level in spleen. In the neonatal life, around 3 +/- 1 days of birth these UsnRNAs' levels again became maximum in all the tissues/organs (except in thymus) followed by decrease up to 5/6 days, and to become steady with slight increase within one to two weeks, when the kinetics of the organ maturation reached to a steady state. In case of thymus, the levels of the U3-U6 snRNAs were high on day 0 of birth followed by decrease in their level on day 1/2 and then increased to become steady within 2-4 weeks; whereas the U1 and U2 snRNAs' levels were high on day 3 of birth and the subsequent changes were similar to that in other tissues/organs. Thus the different UsnRNAs' metabolism in the perturation period and in the early stages of neonatal life has indicated the differential cellular functions in these two stages of development. These alterations in the metabolism of these UsnRNAs might be due to the differential changes in the rate of synthesis of these UsnRNAs and/or with their differential turnover rate in the different stages of development. Also, the differential variations of these UsnRNAs' levels have been observed among the different tissues/organs at the respective stages of development indicating the differences in the UsnRNAs' metabolism among the different cell/tissue lineages. Thus, it can be concluded that the metabolism of these UsnRNAs were developmentally regulated with some cell/tissue lineage variations, which might have some role in the developmentally regulated cellular process of proliferation and differentiation, through altered RNA splicing and processing.

Changes in UsnRNA biosynthesis during rat liver regeneration

Partial hepatectomy (P.H.) induces a partially synchronized growth response of liver under normal regulation of growth. In this phase changes in cellular morphology, radial distribution pattern of cells and other biological as well as major biochemical changes are well documented. Here, we have shown that the cellular content of UsnRNAs altered during this proliferative phase as well. The level of spliceosomal UsnRNAs (U1, U2, U4-U6) gradually decreased by 30-50% upto 48 hrs of P.H. followed by gradual increase to reach the normal level within one month of P.H. The U3 snRNA level on the other hand, was nearly equal to that in normal liver at 48 hrs of P.H. but in 24 and 72 hrs of P.H. its level was high (4 fold) in contrast to that in other UsnRNAs. Thus, it is clear from our data that the level of all the six UsnRNAs decreased during 48 hrs of P.H. compared to that after first 24 hrs. This has been correlated in the kinetics of UsnRNAs' synthesis (in terms of labelling) in isolated hepatocytes, where the rate of labelling of all the six UsnRNAs increased 20-30% in 24 hrs regenerating hepatocytes (R.H.) followed by sharp decrease by 30-50% within next 24 hrs, compared to that in the normal hepatocytes. But from 72 hrs onwards in R.H. the rate of labelling of all the six UsnRNAs again increased by 30-50% (compared to that in normal hepatocytes) followed by decrease of their labelling-rate to reach the normal level in R.H. within one month of P.H.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in UsnRNA biosynthesis during rat liver regeneration

Partial hepatectomy (P.H.) induces a partially synchronized growth response of liver under normal regulation of growth. In this phase changes in cellular morphology, radial distribution pattern of cells and other biological as well as major biochemical changes are well documented [24]. Here, we have shown that the cellular content of UsnRNAs altered during this proliferative phase as well. The level of spliceosomal UsnRNAs (U1, U2, U4-U6) gradually decreased by 30-50% upto 48 hrs of P.H. followed by gradual increase to reach the normal level within one month of P.H. The U3 snRNA level on the other hand, was nearly equal to that in normal liver at 48 hrs of P.H. but in 24 and 72 hrs of P.H. its level was high (4 fold) in contrast to that in other UsnRNAs. Thus, it is clear from our data that the level of all the six UsnRNAs decreased during 48 hrs of P.H. compared to that after first 24 hrs. This has been correlated in the kinetics of UsnRNAs' synthesis (in terms of labelling) in isolated hepatocytes, where the rate of labelling of all the six UsnRNAs increased 20-30% in 24 hrs regenerating hepatocytes (R.H.) followed by sharp decrease by 30-50% within next 24 hrs, compared to that in the normal hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

RNA synthesis and stability in UV-irradiated and nonirradiated mouse L cells

In mouse L cells, relatively low doses of UV light (e.g., about 35 J/m2) induced the rapid breakdown of the molecules of many RNA species transcribed shortly before irradiation. This included 28S, 18S, 5.8S, and 5S rRNA, U1, U2, U3, U4, and U5 small nuclear RNA, but not the main band of transfer RNAs or 7SL RNA. At higher UV doses, an RNA band that contains tRNAleu was also degraded rapidly after UV irradiation. RNA molecules synthesized long before irradiation (e.g., 22 h for small RNAs, 4 h for large rRNAs) were not affected. Our results suggest that the maturation and/or assembly into fully mature ribonucleoprotein particles of several small RNA species is not completed 4 h after transcription. The effect of UV radiation occurred in mouse L cells, but not in human HeLa or KB cells. In a previous report, L cells were transformed by DNA transfection with two mouse U1b RNA genes, named U1.1 and U1.2. We observed now that, in L cells transformed with the U1.2 gene, the ratio of radioactivity in the apparent U1b and U1a RNA precursors after 5 min of labeling was about 20 times higher than a) this ratio in briefly labeled L cells that had been transformed with the U1.1 gene, and b) the ratio of radioactive mature U1b and U1a RNA after 20 h of chase in L cells transformed with the U1.2 gene. These results suggest that very high levels of U1b RNA are transcribed from the exogenous U1.2 gene copies, followed by the rapid degradation of most of these transcripts.