The spindle checkpoint detects errors in kinetochore attachment to microtubules and delays anaphase if attachment is improper. The checkpoint is activated by attachment-sensitive components including @entity26112 and certain phosphorylated proteins detected by the 3F3/2 antibody. We have studied @entity26112 and 3F3/2 immunofluorescence in grasshopper spermatocytes. As in other cells, unattached kinetochores are loaded with @entity26112 and are highly phosphorylated, whereas after proper attachment, @entity26112 is lost and kinetochores are dephosphorylated. What is it about proper attachment that produces these changes--is it microtubule attachment itself or is it the @entity2701 from mitotic forces that follows proper attachment? Using micromanipulation, we created an intermediate state, weak attachment, that provides an answer. Weakly attached kinetochores are not under @entity2701 and have few kinetochore microtubules. Despite the absence of @entity2701 , many weakly attached kinetochores lose their @entity26112 and become dephosphorylated. Therefore we conclude that microtubule attachment determines both @entity26112 binding and phosphorylation. Nevertheless, @entity2701 plays an absolutely essential role. Tension elevates the number of kinetochore microtubules to the level necessary for the complete loss of @entity26112 and dephosphorylation from all kinetochores. This gives a reliable 'all clear' signal to the checkpoint, allowing the cell to progress to anaphase.

Checkpoint signals in grasshopper meiosis are sensitive to microtubule attachment, but XXXX is still essential.

@entity2701 :: ('MESH:D018781', 'Disease') :: ['tension'] @entity26112 :: ('4085', 'Gene') :: ['Mad2']
@entity2701 :: (MESH:D018781,Disease) :: ['tension']
