cAMP-dependent reorganization of the Cajal bodies and splicing machinery in cultured Schwann cells.
It is well established that forskolin-induced elevation of cAMP results in activation of DNA synthesis in Schwann cell cultures. This promitotic response is partially mediated by the Cdk2, which is required for the transition from the G1 to the S phase of the cell cycle. In the present study, we analyze the effects of cAMP elevation in cultured Schwann cells on the transcriptional activity and on the organization of two nuclear compartments involved in pre-mRNA processing: Cajal bodies (CBs) and splicing factor compartments. Our immunofluorescence and quantitative studies show that forskolin treatment induces a 5.6-fold increase in the proportion of S phase Schwann cells, detected by a short pulse (20 min) of BrdU incorporation. This increase in DNA synthesis correlates with an activation of global transcription, as is indicated by the higher nuclear incorporation of BrU in nascent RNA. Forskolin treatment significantly increases the percentage of Schwann cells containing typical CBs, which concentrate spliceosomal snRNPs and the survival motor neuron (SMN) protein. This increase in the number of CBs closely correlates with the activation of transcription. Moreover, the occurrence of CBs is significantly higher in BrdU (+) cells than in BrdU (-) cells, indicating that entry in the S phase promotes the formation of CBs. During the S phase, Schwann cell nuclei display higher Cdk2 nuclear staining and concentrate this kinase in CBs. Forskolin also induces a redistribution of the pre-mRNA splicing factors in Schwann cells. Primary cultures of Schwann cells provide an excellent physiological model to demonstrate that the assembly of CBs is a transcription- and replication-dependent cellular event. Moreover, the S phase accumulation of Cdk2 observed in Schwann cells supports a functional link between CBs and DNA replication, which is mediated by the possible participation of CBs in the regulatory control of histone gene expression.
Fernandez
Rosario
R
Department of Physiology and Pharmacology, Faculty of Medicine, University of Cantabria, Santander, Spain.
Pena
Emma
E
Navascues
Joaquin
J
Casafont
Iñigo
I
Lafarga
Miguel
M
Berciano
Maria T
MT
D000818:Animals; D000831:Animals, Newborn; D042846:CDC2-CDC28 Kinases; D002455:Cell Division / Q000187:drug effects / Q000235:genetics*; D002467:Cell Nucleus / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D020541:Coiled Bodies / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism* / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication / Q000187:drug effects / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D006657:Histones / Q000187:drug effects / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D010525:Peripheral Nerves / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012326:RNA Splicing / Q000187:drug effects / Q000235:genetics*; D016601:RNA-Binding Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D017411:Ribonucleoproteins, Small Nuclear / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D016196:S Phase / Q000187:drug effects / Q000235:genetics; D055532:SMN Complex Proteins; D012583:Schwann Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D055533:Survival of Motor Neuron 1 Protein; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
D017362:Cyclic AMP Response Element-Binding Protein; D006657:Histones; D009419:Nerve Tissue Proteins; D016601:RNA-Binding Proteins; D017411:Ribonucleoproteins, Small Nuclear; D055532:SMN Complex Proteins; C526473:Smn1 protein, rat; D055533:Survival of Motor Neuron 1 Protein; D005576:Colforsin; D000242:Cyclic AMP; D017346:Protein Serine-Threonine Kinases; D042846:CDC2-CDC28 Kinases; C495892:Cdk2 protein, rat; D051357:Cyclin-Dependent Kinase 2; D018844:Cyclin-Dependent Kinases