Existence of nuclear‐encoded 5S‐rRNA in bovine mitochondria

Abstract

A number of proteins functioning in mitochondria are synthesized in the cytoplasm and imported into the mitochondria via specific transport systems. In mammals, on the contrary, mitochondrial membranes have generally been considered to be impermeable to nucleic acids. However, here we show that an RNA with 120 nucleotides, the sequence of which is identical to that of the nuclear-encoded 5s RNA, exists in bovine mitochondria, although the mitochondrial genome encodes no 5s RNA gene. This RNA molecule was found to be retained in purified bovine mitochondria as well as in the mitoplasts, even after extensive treatment with an RNase, demonstrating that the 5s RNA is actually located inside the mitochondrial inner membrane. The 5s rRNA molecule was also shown to exist in mitochondria from rabbit and chicken.

Evidence for the Presence of 5S rRNA in Mammalian Mitochondria

“…Taken together, the Northern, RT-PCR, and transient expression results imply, first, that 5S rRNA is an authentic component of mammalian mitochondria (in agreement with more recent observations regarding the presence of 5S rRNA in bovine mitochondria [Yoshionari et al, 1994]) and, second, that an engineered transcript similar to 5S rRNA can also be imported into mitochondria. We note that the ability to import a synthetic transcript into human mitochondria may allow for the development of new approaches to the treatment of human mitochondrial diseases associated with maternally inherited mutations in mtDNA (Schon et al, 1997).…”

“…Moreover, analysis of the complete mitochondrial genome of the wallaroo, an Australian marsupial, failed to detect any gene for a true tRNA Lys (Janke et al, 1997), which led the authors to hypothesize that, as in yeast , this tRNA is imported into the organelle. Finally, there is evidence that bovine mitochondria contain 5S rRNA (Yoshionari et al, 1994).…”

“…This postulate was proven recently (Rusconi and Cech, 1996), and the import of tRNAs into mitochondria has now been observed in a variety of biological systems, including plants (Phaseolus vulgaris, Solanum tuberosum, Triticum vulgaris, Zea mays, Marchantia polymorpha, and Chlamydomonas reinhardtii), fungi (Saccharomyces cerevisiae), and protozoa (Tetrahymena pyriformis, Paramecium aurelia, Plasmodium falciparum, Trypanosoma brucei, and Leishmania tarentolae) (Schneider, 1994;Kazakova et al, 1996;Tarassov and Martin, 1996, and references therein). Mammalian mitochondria do not appear to import tRNAs, but in addition to the RNA moieties of RNase P and RNase MRP, one other RNA species was recently observed to be associated with mammalian mitochondria: 5S rRNA, which was isolated from preparations of bovine mitochondria (Yoshionari et al, 1994). Moreover, an RNA species with a size consistent with that of 5S rRNA has also been found associated with purified human (King and Attardi, 1993) and mouse (Wong and Clayton, 1986) mitochondria, but neither the exact identity of this species nor its presence as an authentic mitochondrial RNA was established.…”

RNA import into mitochondria and its use in gene therapy

“…Третий тип РНК, импортирующейся в мито-хондрии млекопитающих, -это 5S рРНК [9,10]. Эта РНК обычно является структурной состав-ляющей большой рибосомной субъединицы.…”

Discovery and characterization of Acanthamoeba castellanii mitochondrial 5S rRNA

“…A fourth possibility is that the function of 5S rRNA has been assumed in mitochondria by an extramitochondrial 5S rRNA species imported into mitochondria. In this regard, intriguing recent evidence suggests that nucleus-encoded (cytoplasmic) 5S rRNA is a bona fide intramitochondrial component in animals (Yoshionari et al 1994;Magalhães et al 1998), and that human mitochondria are able to import 5S rRNA (Entelis et al 2001).…”