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group_5_presentation_2_-_progeria [2018/03/02 23:42] bhattvj [Pathophysiology] |
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| The main components of the nuclear lamina are type V intermediate filaments known as lamins that contain a central α- helical rod surrounded by globular N and C terminal domains; the C terminal region contains the nuclear localization sequences (Gonzalez, 2011). As proteins they form coiled- coil dimers that can associate head to tail. These protofilaments then create the final lamin filaments. Lamins can be classified into two types: A- type and B- type. A -type lamins are basic and type B is acidic. Type A are encoded by the LMNA gene with its two isoforms being Lamin A and C. B type lamins are therefore encoded by the LMNB1 and LMNB2 genes (Gonzalez, 2011). | The main components of the nuclear lamina are type V intermediate filaments known as lamins that contain a central α- helical rod surrounded by globular N and C terminal domains; the C terminal region contains the nuclear localization sequences (Gonzalez, 2011). As proteins they form coiled- coil dimers that can associate head to tail. These protofilaments then create the final lamin filaments. Lamins can be classified into two types: A- type and B- type. A -type lamins are basic and type B is acidic. Type A are encoded by the LMNA gene with its two isoforms being Lamin A and C. B type lamins are therefore encoded by the LMNB1 and LMNB2 genes (Gonzalez, 2011). | ||
| Lamin A is affected in Progeria so an understanding of the normal transcriptional and translational mechanisms of this protein is essential (Gonzalez, 2011). In cells containing the normal LMNA gene, prelamin A undergoes post- translational modifications before it is found in its mature Lamin A form. Firstly, the cysteine in the C – terminal CaaX motif is farnesylated by farnesyltransferase. Rce1, an endoprotease then cleaves the three terminal amino acids. Then the newly- available cysteine is then methylated by carboxyl methyltransferase, ICMT. Lastly to create mature Lamin A, 15 C- terminal residues that include the farnesylated and carbosymethylated C- terminal cysteine are cleaved by another endoprotease, Zmpste24/ FACE-1 (Gonzalez, 2011). | Lamin A is affected in Progeria so an understanding of the normal transcriptional and translational mechanisms of this protein is essential (Gonzalez, 2011). In cells containing the normal LMNA gene, prelamin A undergoes post- translational modifications before it is found in its mature Lamin A form. Firstly, the cysteine in the C – terminal CaaX motif is farnesylated by farnesyltransferase. Rce1, an endoprotease then cleaves the three terminal amino acids. Then the newly- available cysteine is then methylated by carboxyl methyltransferase, ICMT. Lastly to create mature Lamin A, 15 C- terminal residues that include the farnesylated and carbosymethylated C- terminal cysteine are cleaved by another endoprotease, Zmpste24/ FACE-1 (Gonzalez, 2011). | ||
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| - | {{:screen_shot_2018-02-25_at_10.38.01_am.png?200|}} | ||
| - | Figure 10: The mammalian nuclear envelope- representation of the nucleus showing lamins, nuclear pore complexes, the inner and outer nuclear membranes and associated proteins. | ||
