Cytoplasmic assembly of snRNP particles from stored proteins and newly transcribed snRNA's in L929 mouse fibroblasts

Journal Article · Wed Jun 01 00:00:00 EDT 1988 · Exp. Cell Res.; (United States)

DOI:https://doi.org/10.1016/0014-4827(88)90336-9· OSTI ID:6908835

Sauterer, R A; Feeney, R J; Zieve, G W

Newly synthesized snRNAs appear transiently in the cytoplasm where they assemble into ribonucleoprotein particles, the snRNP particles, before returning permanently to the interphase nucleus. In this report, bona fide cytoplasmic fractions, prepared by cell enucleation, are used for a quantitative analysis of snRNP assembly in growing mouse fibroblasts. The half-lives and abundances of the snRNP precursors in the cytoplasm and the rates of snRNP assembly are calculated in L929 cells. With the exception of U6, the major snRNAs are stable RNA species; U1 is almost totally stable while U2 has a half-life of about two cell cycles. In contrast, the majority of newly synthesized U6 decays with a half-life of about 15 h. The relative abundances of the newly synthesized snRNA species U1, U2, U3, U4 and U6 in the cytoplasm are determined by Northern hybridization using cloned probes and are approximately 2% of their nuclear abundance. The half-lives of the two major snRNA precursors in the cytoplasm (U1 and U2) are approximately 20 min as determined by labeling to steady state. The relative abundance of the snRNP B protein in the cytoplasm is determined by Western blotting with the Sm class of autoantibodies and is approximately 25% of the nuclear abundance. Kinetic studies, using the Sm antiserum to immunoprecipitate the methionine-labeled snRNP proteins, suggest that the B protein has a half-life of 90 to 120 min in the cytoplasm. These data are discussed and suggest that there is a large pool of more stable snRNP proteins in the cytoplasm available for assembly with the less abundant but more rapidly turning-over snRNAs.

• Research Organization: SUNY, Stony Brook (USA)
• OSTI ID: 6908835
• Journal Information: Exp. Cell Res.; (United States), Vol. 176:2
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
NUCLEOPROTEINS
BIOSYNTHESIS
BIOLOGICAL HALF-LIFE
CELL CYCLE
CELL NUCLEI
CYTOPLASM
FIBROBLASTS
HYBRIDIZATION
L CELLS
LABELLED COMPOUNDS
METHIONINE
MICE
PRECURSOR
RADIOIMMUNOASSAY
RADIOISOTOPES
RNA
TRACER TECHNIQUES
AMINO ACIDS
ANIMAL CELLS
ANIMALS
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CONNECTIVE TISSUE CELLS
DRUGS
IMMUNOASSAY
IMMUNOLOGY
ISOTOPE APPLICATIONS
ISOTOPES
LIPOTROPIC FACTORS
MAMMALS
NUCLEIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PROTEINS
RADIOASSAY
RADIOIMMUNOLOGY
RODENTS
SOMATIC CELLS
SYNTHESIS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques