Assembly of monic acid is continued by the transfer of the 12C product of MmpD to MmpA. Two more rounds of extension with malonyl-CoA units are achieved by module 5 and 6. Module 5 also contains a KR domain. Post-PKS tailoring
The keto group at C3 is replaced with a methyl group in a multi-step reaction (Figure 3). MupG begins by decarboxylating a malonyl-ACP. The alpha carbon of the resulting acetyl-ACP is linked to C3 of the polyketide chain by MupH. This intermediate is dehydrated and decarboxylated by MupJ and MupK, respectively.The formation of the pyran ring requires many enzyme-mediated steps (Figure 4). The double bond between C8 and C9 is proposed to migrate to between C8 and C16. Gene knockout experiments of mupO, mupU, mupV, and macpE have eliminated PA-A production. PA-B production is not removed by these knockouts, demonstrating that PA-B is not created by hydroxylating PA-A. A knockout of mupW eliminated the pyran ring, identifying MupW as being involved in ring formation. It is not known whether this occurs before or after the esterification of monic acid to 9-hydroxy-nonanoic acid. The epoxide of PA-A at C10-11 is believed to be inserted after pyran formation by a cytochrome P450 such as MupO. A gene knockout of mupO abolished PA-A production but PA-B, which also contains the C10-C11 epoxide, remained. This indicates that MupO is either not involved or is not essential for this epoxidation step.
About 2-3% of osteosarcomas, 9% of rhabdomyosarcomas, and 7-20% of patients with multiple primary tumours have p53 mutations.Although most cases of this syndrome have early onset of cancer, cases have also been reported later in life. Diagnosis
Li–Fraumeni syndrome is diagnosed if these three criteria are met:

The patient has been diagnosed with a sarcoma at a young age (below 45). A first-degree relative has been diagnosed with any cancer at a young age (below 45). Another first- or a second-degree relative has been diagnosed with any cancer at a young age (below 45) or with a sarcoma at any age.Other criteria have also been proposed:
A proband with any childhood cancer or sarcoma, brain tumor or adrenal cortical carcinoma diagnosed before age 45
A first- or second-degree relative with a typical LFS malignancy (sarcoma, leukaemia, or cancers of the breast, brain or adrenal cortex) regardless of age at diagnosis
A first- or second-degree relative with any cancer diagnosed before age 60A third criterion has been proposed:
Two first- or second-degree relatives with LFS-related malignancies at any age. Management
Genetic counseling and genetic testing are used to confirm that somebody has this gene mutation. Once such a person is identified, early and regular screenings for cancer are recommended for them as people with Li–Fraumeni are likely to develop another primary malignancy at a future time (57% within 30 years of diagnosis).